I just ordered an ASUS Rampage II Extreme from China, at a decent £115. Hopefully it will work and I can be back within first match. Don't think It'll be ready for draft day as shipping is gonna take a while, but don't let that scare ya capitanos..! I'm not looking forward to replace it and reinstall Windows and all the shit that follows.
I'd run stress tests over night. I know you did memtest but how long you kept it going for? Also get prime95 and run it so you can see if your cpu fails. Only way I'd change motherboard is if i know 100% that's that problem. Also never tried a new PSU, old one might not be good enough for your current system.
Keung if your outlets' voltages are fluctuating that badly, it might end up damaging your new board as well. Are you using a surge protector? If not, I'd go ahead and get one. And hell, I can't help but wonder if your pc is automatically shutting itself off when the voltage fluctuates to prevent damage, or it could just be shutting off unintentionally because of it. Either way, try using a surge protector and see what happens. That would be really lucky though if that's the case.
if that kind of voltage is 'normal' for your area that's pretty fucked up. consider what anguis said, get a UPS that is always-on (like a filter) and the voltage should be stable. would help your psu too
Sam, I ran MemTest for about 10 passes. I didn't see any reasons to keep going at that point (no errors)
The overvoltage error was in my last apartment, not where I live now. The technician blamed the power company because the power had a habit of "blinking" a bunch. Anyway, I should probably get myself a surge protector either way. I don't know why I haven't got one yet, laziness I suppose.
If you had the same PC at your old apartment and these issues occurred back then, either the power company or your old apartment complex owes you a new pc!
Sam, it won't stay on for longer than 30 minutes, so I am unable to run Prime95 I'll wait for the new mobo, hopefully it'll fix it, otherwise I'm going to cry for more help!
Thanks for all the input so far, guys! Appreciated!