It's definitely not the fans since I've tried stopping each one temporarily, so signs seem to be pointing towards the PSU?
With that in mind, I was wondering if anyone could please recommend a good one for an i7 CPU, 5750 graphics and 8GB RAM? Preferably one that's modular, quiet, reliable and cheap I have a Dell Vostro btw.
Both will power the system without problems. Antec is a very good brand.
That being said, one potential pitfall is that you may not be able to put them into the case without modifying the case (as in the mesh in the case may cover up the port to plug the power cord into the back of the PC).
The only way to avoid this problem is to modify the case with metal cutters (labor intensive, cheap, potentially ugly) or to buy a PSU from Dell (expensive).