Pasi123

I think that's just some extra VRM cooling. Older boards like the P8P67 Deluxe, P8Z68 Deluxe, P8Z77-V Deluxe had it too and so did the newer Z170 Deluxe

Should work fine if it's a good quality 550W PSU and has a 8-pin PCIe power cable.

Phenom II X6 1100T @ 4GHz+ and GeForce GTX 580's in SLI. That's what was available in December 2010 when the 1100T was released.

Depends on if the case comes with a RGB controller or not. If not then you could buy a controller that connects to an internal USB 2.0 header. The motherboard itself predates ARGB by multiple years so it doesn't have an ARGB header.

Not really worth it unless you already have a X99 board (or want to play around with one), but even then for gaming a 8c/16t Xeon E5-1660v3 or E5-1680v3 would be better because they can be overclocked.

That board doesn't have a M.2 slot but it does support NVMe boot so that is something that could be easily added with a PCIe card. Though like you said if it's running fine there is no need to upgrade. The difference between NVMe and SATA SSDs isn't that big in normal use. Another thing mentioned in this BIOS update is support for a USB 3.1 (10Gbps?) add-on card, but for upgrading to that to make sense you'd need to have some USB devices that benefit from speeds faster than USB 3.0 5Gbps. Same thing for network cards, you'd need a network faster than 1Gbps for any 2.5Gbps or faster NIC to make sense.

Have you tried all of the sticks and slots individually? Just because all the sticks show up in BIOS doesn't mean they all work

While you can install Windows 11 on unsupported CPUs without needing any bypass if you have a TPM 2.0 module, you will not be able to install the yearly updates (like going from 23H2 to 24H2) through Windows Update because it checks if you have a officially compatible CPU (Which would be Intel 8th gen or newer or Ryzen 2000 or newer). There is ways to bypass that but it doesn't differ from not having TPM 2.0 so IMO it's completely pointless to buy a TPM module for Windows 11 compatibility if you have an unsupported CPU. Newer CPUs have Intel PTT or AMD fTPM so no TPM module is required on the motherboard or if you have a CPU without TPM but TPM 2.0 module then that would be fine too. Though I'm pretty sure all of the officially supported CPUs have PTT or fTPM

I had a GTX 660 as my main card in 2014-2016 paired with an i7-920 and later i7-950. Anything from 2010-2015 should run fine at 1080p above 30fps. The Kepler architecture didn't age that well so a lot of newer games don't run as well as on some other cards that are comparable to the GTX 660 in older games. In some games cards like a GTX 960 can perform similarly to a GTX 780 (Ti) or even beat it, and of course there's games that won't even boot on the Kepler 600/700 series cards due to lacking proper DX12 support. I have recently tried Genshin Impact and Honkai Star Rail on the GTX 660. Both of them run fine on it, 1080p around 60fps with low to mid settings. Though Genshin is a bit CPU intensive so even an i7-3770 @ 4.22-4.43GHz was hitting over 50% usage. Though what you can play on your PC also depends a lot on what CPU you have.

The lower PCIe x16 slot is electrically only x4 according to the manual

Yes, the E5-1680 v2 is better than the E5-1650 v2. Both of them are overclockable and the E5-1680 v2 has 2c/4t more than the E5-1650 v2. It also has 25MB L3 cache instead of 12MB. But if you run them at stock then the locked, but cheaper, E5-2667 v2 would be tiny bit faster. Overclocked E5-1680 v2 would of course be quite a bit faster

UEFI didn't became a common thing until 2011-2012 on Intel 2nd and 3rd gen. Though some LGA1155 boards didn't have UEFI. But even then that was over a decade ago. Nowadays it's best to disable CSM unless you have some hardware or OS that doesn't work in UEFI mode In the early Ryzen days (2017-2018) Windows would default to install in legacy mode but as far as I know it should now default to UEFI mode because of all the Windows 11 requirements etc.

Windows 10 (and 11) is extremely slow on hard drives, the last one that worked fine on HDDs was Windows 8.1 but even then the speed difference between SSD and HDD was huge. The 4GB RAM makes it even worse because the OS can't cache things in to RAM when there's barely enough RAM for the OS and programs. And when the system is out of physical memory it uses the page file on the slow HDD. SSD is a must for modern operating systems and so is 8GB RAM. For more modern PC's I'd say 16GB is the absolute minimum. Even though the i5-2500 is now 13 years old it should still be powerful enough to not feel slow doing normal tasks. Though of course it won't be as snappy as decade newer CPU's

The iGPU in the 4th gen i3 is much better than the GeForce 210. The 210 is a display adapter from 2009 and uses a really low end GT218S chip from 2007

That would only be a problem in newest of the newest games. My X5670 @ 4.4GHz + GTX 1080 had no problems running older games games like Red Dead Redemption 2 and Shadow of the Tomb Raider. And newer but lighter games like Genshin Impact and Honkai Star Rail run great at max settings