How much upgrade headroom with 500W PSU?

[Jd007]

Hi all:

Here's my current setup:

Core i7 920 w/ Cooler Master V8 (no OC)
Gigabyte EX58-UD5
G.SKILL 3x2GB DDR3 1333
1xATI HD4850 512MB w/ Thermaltake DuOrb heatsink
6xHDDs (3x1TB, 1x2TB, 1x400GB, 1x320GB)
1xDVD burner
Antec 300 w/ 1x120mm rear and 1x140mm top fan

I'm running the above setup perfectly fine using a 4-month old OCZ ModXStream 500W PSU, which has two +12V rails rated at 18A each.

I was wondering what would my upgrade headroom be, in terms of new graphics cards, with that PSU and that system (obviously I want my computer to be stable under full CPU and GPU load)? I think I can definitely switch up to a 5850, but not sure about 5870 or GTX 275. Does anybody have enough experience to give me a relatively accurate answer? This would determine whether my next upgrade would be just GPU or PSU + GPU.

And what if I plan to OC the CPU? Nothing crazy, just to maybe 3.4 Ghz.

Thanks in advance!

 

[Lunyone]

Well with 36A on the combined 12v rails, I think even a 5870 would do. Now with OC'ing the 920 too, I'd be a bit cautious with that too, but should be fine with the GPU upgrade.

 

[Jd007]

Thanks Lunyone. What about for nVidia cards like GTX 275/285? Also from what I heard Fermi cards are going to use much more power. I'm waiting for GTX 300 series to come out and see if it's better than 5800 series.

 

[qazwsxokmijn]

Yeah, a 5850/70 should fit in fine with the PSU though personally I'd upgrade the PSU as well.