Ok,finally managed to get them to replace it with a corsair cx600 PSU. voltages are pretty much stable now i guess, Bios says
cpuvcore - 1.352v
3.3v - 3.296
5v- 5.016v
12v- 11.968v
corsair CX600
Temp is at around 33c system temp and 36c cpu core temp
My comp boots up fine now, however, the 2nd half of my problem , the issue with my comp restarting when i play world of warcraft and/or use firefox, persists.
Strangely when i play games such as call of duty Modern Warfare etc, on max settings at 1920x1080, the computer is very stable.
Going to post on world of warcraft forums to find out, but since it also crashed when i used firefox, i wonder if its an issue with the drivers or something?
Updated catalyst drivers for my sapphire HD5750 recently and will try updating BIOS drivers today. anything else that could cause this?
UPDATE: instead of crashing, my comp went into a hard lock, or hard freeze today when i tried opening world of warcraft.
EDIT: looking through the event logs, i found 2 common issues that kept reappearing. after searching the net, i found someone else who had a similar problem
http://www.techspot.com/vb/topic131382.html