I'd imagine you'd be fine.
I've run a dual core AMD PC with a 7800gt on a 250w delta branded psu in the past with no issues.
The 6600gt will certainly not draw more and i don't think the 6800gt would either.
Power supply ratings for GP's are generally a joke anyway.
My old PC ran an e2160 @ 3ghz and an ATi 3870X2 - at idle the PC used 189w and used 327w at full tilt.
Only thing to look out for is the 12v rails amp rating on the PSU - if you have that info we could probably say yay or nay for running it on your hardware. Also, the model of the PSU would be helpful too!
gt
I've run a dual core AMD PC with a 7800gt on a 250w delta branded psu in the past with no issues.
The 6600gt will certainly not draw more and i don't think the 6800gt would either.
Power supply ratings for GP's are generally a joke anyway.
My old PC ran an e2160 @ 3ghz and an ATi 3870X2 - at idle the PC used 189w and used 327w at full tilt.
Only thing to look out for is the 12v rails amp rating on the PSU - if you have that info we could probably say yay or nay for running it on your hardware. Also, the model of the PSU would be helpful too!

gt
...hope u do...thanks...