Instability problems, suspect PSU problem

[AeonGrey]

First off, here is a list of my hardware:

Antec Sonata II case
550W S12 Seasonic PSU w/ 4 rails, 18A each rail
ASUS P5N-E SLI mobo
Intel Core2Quad Q6600
eVGA GTX 260 core216 video card
2 sticks of 2GB DDR2 RAM 800Mhz
1 SATA 500GB Seagate HD
1 IDE DVD-RW drive
1 120mm fan in rear

These problems all started when my original video card died, after which I decided to go ahead and upgrade. Basically, I kept the motherboard and RAM and ordered a Q6600, the GTX 260 and a cheap OCZ 500W PSU. After getting this setup working, I started getting problems with the computer randomly resetting. No blue screens, no noises, no error logs upon rebooting, nothing. Eventually I realized my PSU wasn't really adequate for the card, so I bought a Seagate 550W PSU with 4 12V rails that each have 18A. The card officially requires 36A on the 12V rails, so I figured this would be fine. And it is BETTER, but the problem is still happening. I am not overclocking ANYTHING. CPU, video card, fans, voltages and everything are all at detected BIOS defaults. I even updated to the latest BIOS. I am still getting these random non-blue-screen resets when playing games. It doesn't happen EVERY time, but usually after about 15-30 minutes of playing any kind of graphically intensive game, bam, resets. I've tried gaming with temperature monitors running in the background to set off alarms when gpu, cpu or mobo temps get up too high. Nothing is running hot. I really dunno what to do, I've already gone through one PSU upgrade to something that I thought would be adequate, and as far as I knew Seasonic was a good PSU brand. Do I need to go even HIGHER? Could this be some kind of strange electrical problem, can anyone recommend I try anything with the way the motherboard is secured in the case? I'm really at my wit's end.

Thanks for any help.

 

[BoBBYI986]

sounds like PSU is not powerfull enough, recommendation for running a gtx 260 is 650 - 700w. If you have any friends with spare 650 - 700w power supplies ask em to borrow it and try it on ur system, see if it fix's ur problem.

Also check your ram, run prime 95, run mem test. see if you have any faulty ram and stability issues.

 

[AeonGrey]

sounds like PSU is not powerfull enough, recommendation for running a gtx 260 is 650 - 700w. If you have any friends with spare 650 - 700w power supplies ask em to borrow it and try it on ur system, see if it fix's ur problem.

Also check your ram, run prime 95, run mem test. see if you have any faulty ram and stability issues.

Yeah, I have been able to run the system okay in Prime95 and even on other stress-test programs that fully use all 4 cores of the Q6600. I've also run memtest on my RAM for hours on end with no issues. The only other explanation I can come to is that it's the PSU. I suppose I could try another but damn, this is the LAST psu I'm going to buy.

 

[BoBBYI986]

oh yea dude befor you go and buy a new psu try running 3dmark, see if its the same and restarts it self, if it does personally i would think the card is suckin to much power when in use, more than ur psu can handle therefor causing system restarts. 550w psu on a gtx 260 is cutting it fine.