i'm getting new gamning rig soon, but i dno that much abt psu's. any1 noe any good brands? (i've got thermaltake and antec on my list) (plz, no generic ones)
also, s 650 watts overkill for a rig with
2 x 7900GT's x sli
athlon 64 4800+ X2
a dvd burner
xfi sound card
(all the rest network, usb etc r onboard)
Nearly any PSU out there would do the job just fine.
Real power problem arrise from double, triple, or quadrupling a single power jack off of a smaller power-supply. It's not really a problem to leave jacks hanging inside the computer unused. Maybe you'll find a use for them later.
You wouldn't want a large power-supply in a small computer though, because you will spend thousands powering a computer that would otherwise only require a few hundred dollars for many years of service.
It's a give and take. The simple way is to count how many pieces inside the computer need power. Make sure you select from the list of motherboard compatible power supplies availible, and choose the one that will power all of your other devices without leaving a power cable hanging free, and that's a good way to make sure that you aren't converting a bunch of power that won't be used. I'm not an electrican but I've never really had much trouble, except where I jacked too many devices into too little a power-supply, and that caused serious system instability.
650 might be a lil overkill, probably 450-500W would suffice, but with dual video cards, and a dual core cpu you'll want a little extra in the power dept. anyway
I wouldn't worry about your power bill as the pc won't be constantly drawing 650W, thats just what it is capable of drawing..it will only actually use what power the combined components of the system request.
You could always buy a PSU and see if it will handle the stress, and if it wont' even plug everything in the take it back and get the next step up and so on until you find the one that works best. Just remember that the PSU's hardest fit is going to be on the motherboard, so make sure to get a PSU that fits that connector first, and has all the other plugs you need.
Good luck in building your computer, but I can't advise you strongly enough to do your homework on each part as it will pay off in the end.