hello could anyone give me some advice i have an m3n78 pro motherboard 1 sata harddrive 500gb and 1 sata hardrive 80gb a geforce 9800gtx graphics card a phenom 2 940 overclocked to 3.30 ghz and the coolmaster v8 cpu cooler 2x2 OCZ Gold XTC OCZ2G8002G and a dvd rom and the therrmaltake spedo advance case with all 8 fans on what would be a good power supply for the set up i want 80 plus and sli certified and what wattage would be sufficient for it thank you for any advice
SLI certified shouldn't be a factor, there are many non certified power supplies that will power your system with either 1 or 2 cards.
A good quality 550w or 650w from the Corsair TX series would do for a single 9800GTX, for SLI I'd look at 750 watts from the same line or others such as the PCP&C Silencer.
If you are planning on using the psu for a while and upgrading to more powerful cards an 850 watt unit would be better suited.
^5 and +1 for what DellUser1 said.
Corsair has a well deserved reputation for high quality power supplies. They consistently earn high marks in technical reviews and comparisons. The units are very stable and reliable. It is one of three or four brands that are aften recommended by veteran posters at this forum.