DogKnight

Good to know. SSD's are the best upgrade possible to anything with a mechanical HDD. Just a note that if you're still thinking of upgrading the CPU, do your research. Most Apple computers use non "K" variants of CPU's. E.g. It would use the i7 7700 and not the i7 7700K. The main thing to look into is the power available to the socket and whether or not the socket can provide for the TDP of the CPU you're planning on using.

It will most likely work. You should be able to access the full 20gb. Downside will be a slight loss of performance. LTT did a video on this in the past, have a watch of that one. Edit: Found the video.

I use a Netgear XS508M. 8 Port, 10gbe, RJ45. Not cheap. But definitely not the most expensive. I believe rack mount brackets can be added to it.

Handy tool for installing current versions of OSX/macOS on unsupported Macs. https://dortania.github.io/OpenCore-Legacy-Patcher/ Be aware of potential performance issues, especially if your GPU does not have metal support. If the above does not make any sense, ignore this post and stick to 10.13.x.

Johnny Bigg has good options. Including options for those that are just tall and those more rounded. Worth checking out if you haven't already.

Some of this is what I am looking at doing for a 2011 iMac my daughter uses. That MacRumors thread is a great resource for GPU upgrades. Be aware that there are different physical sizes for the MXM GPU's (MXM-A and MXM-B). Depending on your existing spec will depend on what GPU heatsink you have in your device and will determine what fits or what needs to be modded to make it fit. The other forum covers a lot of this in a lot of detail, so definitely read up on it. The biggest problem holding these machines back is the GPU's. Not due to power, but the support for the metal API. When Apple introduced the requirement for metal support, it dropped support for any iMac prior to the 2012 model. This limits the OS to 10.13.x. By upgrading the GPU, depending on the model, you can update the machine to a current version of MacOS. This of course brings in support for newer apps across the board. Another neat upgrade you can do is to upgrade the internal WIFI / BT card. If you are going down the GPU route I would invest in this. Allows for features such as handoff and airdrop to be supported. Installing a SSD is the best upgrade you can do if you haven't already. Just be aware when changing drives in these machines they have unique temp sensors for the drives and you will need to get a compatible one for the replacement drive or all the fans will just ramp to max all the time. OWC had kits where you could get a replacement temp sensor. Otherwise the fans can be controlled via software once the OS boots (Mac Fan Control). CPU upgrades can be a bit tough. Need to make sure the replacement CPU has the same TDP / Power Draw as the model you're replacing. Definitely research this one more before you go and order one. I have recently ordered a WX7100 GPU and a replacement WIFI/BT card. Will see how the upgrade goes.

I really only see your options as Threadripper or Xeon options as all consumer range chips are limited. For Intel, the x299 platform topped out at gen 3 PCIE. So you would need to look at Xeon CPU's due to the lack of HEDT options. New workstation CPU's are on the way but I don't believe a date has been confirmed. These CPU's are a step above what would have been previously considered HEDT and are more like high speed Xeon's. For AMD, you have threadripper. Which really seems like your best choice if you want more lanes of PCIE gen 4. Probably worth investigating previous generations as the TR Pro chips are quite expensive.

It seems the motherboard suits 5th gen Ryzen CPU's. So they are your best bet. Find one that fits within your budget. They will all be a big upgrade over your current CPU. Heaps of different reviews out there as well to compare CPU's. I would potentially avoid the higher end SKU's (5900x / 5950x). Due to board age, VRM's, etc. I would recommend looking at one of the following: 5600, 5600x, 5700x, 5800x, 5800x3D. The 5800x3D still compares very well with 13th gen Intel and 7000 series Ryzen CPU's when it comes to gaming performance.

TBH it looks like you've thought things through pretty well. If you intend to be at this house for a long time the best you can do is future proof your wiring in your walls as best as possible by going to the highest end networking cables within a reasonable price. Not that I would expect FTTP to surpass 1gb anytime soon, but mainly for connectivity between devices. It doesn't look like you have a huge area to cover, so probably don't need a mesh setup. A standard wireless router and maybe an access point should have you covered. Will also allow for a bit more flexibility when it comes to upgrading these down the line. Currently I use a Netgear RAX120 and a separate access point with my FTTP. Have a few points in the house wired with Cat 6a. Just not to the extent that I would have liked as this has all been added to an older house. Utilise the rack you're planning on getting. Synology produce rack mounted versions of their NAS' that you could use to cover the security cameras and plex server. I don't understand the need for HDMI/DP in every room. What's the source? Why does it need to be direct instead of just being accessed over the network? The best advice I can give is really to watch all the videos Linus has done on his 'new' house. Should give you some good ideas.

There is a possibility future updates will further improve memory compatibility. And it's likely that any performance difference will not be noticeable outside of synthetic test results. The faster memory is, the more likely you are to have incompatibilities. May resolve itself when you get a dedicated GPU. May have to wait this one out for a while. 6000 mt/s is still a good speed.

Both models being in the 'plus' model range will handle plex quite easy. It depends how much transcoding is required and at what resolution. If you want a couple people in your house to be able to watch 4k content that's transcoded on the fly, the 220+ may struggle a bit due to the lower spec CPU, especially once you consider other background tasks. If its just you however, the 220+ will probably do the trick.

I have a few NIC's based on the Intel X550 chipset. They run at PCIE 3.0 x 4. Full 10gb speed is not a problem.

General best practices are your best bet. - Make sure accounts have unique and strong passwords (password managers make this possible) - Use different email accounts for different services. E.g. accounts for random forum signups, different accounts for gov services or finance - Use 2FA wherever you can. Use a token generator and not SMS if possible. - Don't download anything from a less than reputable site - Have some anti-malware solution running. This could be defender or another vendors solution. - Separate guest network for visitors and / or IOT devices. - Keep everything updated. Most updates contain security fixes. There are lots of articles out there that cover best practices and I am sure there are many I have left off. Often criminals go after the weakest links. They often use 'spray and pray' approaches. In other words, they spread their efforts far and wide and hope for results. You just need to make sure you are doing more than the average person. I forget the wording, but there was a good quote that sums it up well. "If you and someone else are being chased by a lion, you don't need to run faster than the lion to survive, you just need to run faster than the other person." If you do want to learn more and look at adding security to your environment; Sophos offer a free home version of their XG Firewall which you can install on an old PC. More than anything this could give you some insight into traffic on your network. You can download it here: https://www.sophos.com/en-us/free-tools/sophos-xg-firewall-home-edition Hope some of this is useful.

Having looked at these two models myself, the main things it comes down to is whether the Xeon is preferable over the Ryzen, and whether or not you intend to use the 10gbe NIC. The XS includes a 10gbe NIC as well. For my use case, its cheaper to go with the regular + model and then upgrade the RAM & NIC. Costs of NVME drives for cache and HDD's remain the same regardless of version. As for performance, unfortunately I can't add anything. I don't use my NAS for VM's at all. My current 920+ is fast enough for my needs. I am mainly looking at the upgrade for additional drive capacity and 10gbe.

Nested Virtualization will be fine. If you were wanting these servers to actually provide services, it may get a bit slow, but as this is just a training lab it should be fine. It will also make it easier with shutting down and restarting hosts, performing upgrades, etc. And it helps alleviate some of the hardware issues you run into with running ESXI on bare metal. I was not able to install ESXI on a NVME drive on my home lab either (either directly on the motherboard or via a PCIE expansion card). I am running it on bare metal myself but I have the benefit of permanent licenses. Only thing I would recommend is more RAM if possible for your system. While many VM's will run with 4gb of RAM, being able to give them 8gb or more will make them more responsive. I am using an older X99 based platform and was able to pickup a relatively cheap 128gb of 2133mhz RAM online. The extra RAM capacity is more beneficial in my use case than faster RAM.