Ok, update: using this thread and some very helpful buying suggestions I successfully built my new pc from scratch. Now everything has been working except for one very annoying thing.
I have this exact case:
http://www.phanteks.com/enthoo-evolv.html
and this motherboard:
https://www.amazon.co.uk/gp/product/B014SL2XKQ/
Now, at first I thought everything was ok. PC temperatures are all good, graphics card works like a charm, no big issues. However there was something I found odd, when I clicked on the speaker icon in windows it would flicker and for a brief moment I would see the audio outputs change. This didn't seem to be a big issue because I can generally hear stuff coming out of my speakers ok.
Fast forward to today: sometimes I notice audio stutter when watching videos, it's kinda hard to pick up on but definitely there. So I installed realtek audio drivers and found my issue. The realtek audio manager keeps showing the front headphone and microphone jack having connection plugged and unplugged.
Now we come to the part why I showed my mobo and case. The front jacks can only really be the audio connections on the case (and not the mobo connections). So I actually connected headphones to this jack, and it still seems to work. I even opened my PC back up and re-checked the connections to make sure it is secure.
Any help would be greatly appreciated, at this point I'm considering calling up the manufacturer of the case. But even then I have no idea whether it's the mobo or case I'm having a problem with.
Here is the cable for the case and the port on the mobo I'm placing it into: