Better have a High Rail 12v for that 7600GT if 300watts.
You can get a cheaper 500w for $39 or so if you search.
I have a cheapo and it's held up well.
(That Bestec 300w PSU that comes with most Compaq's and E Mac's are kinda short for the long haul. Trust me, I know!)
Just make sure it's built well and has all the major connections.
(tether wrapped cords if possible)
Usually the Mom n pop shops have the better deals on those as opposed to Comp USA where the avg joe psu runs ya $65 no matter what.