bigsaucybob said:350w would be fine but just to be safe get 400w or higher.
maroon1 said:no no no, the 128MB 6600 GT is better than 256MB 6600, it was proved by benchmarks
6600 is 300/500 and 8 pipes
6600 GT is 500/1000 and 8 pipes
so the 6600GT is better
anyway ask anyone about who is better 128MB 6600GT or 256MB 6600, and he (or she) will tell u that 6600GT is much better, because the 6600GT has faster clock speed and memory speed, and the extra ram in 6600 is not important , it doesn't increase performance.
and video cards are not measured by memory, it is measured but pipe line , clock speed and memory speed
the gt is the better card, its all over the net you only need to search on google for a fairly quick answer. some cards actually suffer when moving to higher amounts of memory cos they sometimes use memory with worse timings.
i would say that you should go for a PSU rated for at least 450 watts. i like enermax PSU's but there are a lot of good brands to chose from.
Have a look at PSU101 for recommendations
that system you have there is classic overclocking material, which i'm assuming you intend to do