Cakeman

So 10/100/1000 means that you will be able to accept at most 1000MB's a second from whatever source it is feeding from. The highest number is the top speed you will be able to actually use while running that device. 
 
I have 1Gb/s internet, so at most, my 10/100/1000 Ethernet port on my PC that is connected directly to my router can accept ~880Mb's a second.

you can get a powered sub or amp just for the sub, use 3.5mm to single rca for reciever most only have 1(cant think of actually name right now
 
and yes 3.5mm(pc) to rca(reciever) for front, same for rear, same for center
 
or you can use hdmi(pc) to reciever then to tv/monitor but this can have high latency if i remember correctly

Motherboard doesn't help a bit at this stage. It only connects the audio receiver to the motherboard.
Now the thing is that many receivers work properly with speakers rated at 8 ohms which is good. The bad thing is that your sub is rated only 3 ohms and you'll have to find out for a receiver that could go that low without blowing some parts of the receiver. 
I actually found this receiver https://www.ebay.com/p/Pioneer-VSX-520K-5-1-Channel-125-Watt-Receiver/81702086?iid=332523877122 
It can handle from 6 ohms to 16 ohms. The thing is, if you install your sub then you'll blow some electrical part. You either change the woofer of the sub(with one with a bigger resistance 6ohms+) which is a bit complicated or search for another receiver that can work with your sub.

It turbo boost when it's needs to and slightly fluctuates in that range until the task is complete, then it drops to its minimum state. Can fire up cpu-z and a stress test, game, or Cinebench R15 to see for yourself.

Honestly, just get a new phone at this point. You could spend that $25 for a new battery, but it might even be just outdated hardware and no further in-depth software testing on iPhone 5's that will cause even more issues down the line. 

You don't really need 3200 mhz ram dog. 2133mhz will be absolutely fine for a 1400 with what I am assuming is probably a nvidia 1050ti-1060 card.
 
https://pcpartpicker.com/product/JW4NnQ/crucial-memory-ct2k8g4dfs8213
 
You don't need speeds past 2800 mhz until you have a 1070 or higher, and even with a Ryzen 1400, the processor could not take advantage of infinity fabric. 
 
Buy this ram and save yourself money for maybe a Ryzen 1500.