As for the Power Supply question, i dont think ATI cards need a higher power usage. When they say reccomend over 500W or whatever thats total RUBBISH. To give you an idea.. My Pc Spec is similar to yours, Core 2 Duo E6300 1.86Ghz, ATI X1950Pro Turbo, 2GB PC5300 ram. And what power supply am i running on... a 400W NorthQ one. I have had no problems of power shortage at all yet.
ATI probably have higher wattage recomendations so they get less complaints of card failure with the power supply, simple really. I might be wrong they might use more power but i dont think they do on a personal level. If youve got a power supply of a Good quality (A branded one preferably) and its >400w i wudnt worry.
What graphics card are you currently using anyway Rook1e ?,
Whatever it is im sure the 7950GT will please you.
Thanks, anymore questions please either post back here or PM me for a quicker response.