If you want to objectively, accurately and scientifically determine what PSU power is required for your Vid card and PC in both watts and 12v rail amps., the forum Utility link below will show you how easy it is to calculate this information and objectively determine which PSUs are quality built, reliable PSUs that can meet your needs. Be advised that the available 12v rail amps. is just as important as the total PSU wattage. You need both to be correct.
A 500-watt power supply should be able to handle the first card. I don't know AMD well so someone else should verify. I do know that, if you intend on using CrossFireX, you'll definitely need a bigger PSU than 500W. Age shouldn't matter too much, provided it has all the required cables.
thanks for all your inputs, i think im going to buy the 6950 for now and get a better psu down the road. I dont ever plan on going crossfire. Im just concerned if it doesnt have enough power it might fry half my pc, but then again i dont know much at all about power supplies, other than watts. again thanks
There are tutorials around that covers the basics of power supplies. In the "power supplies, ..." category, there's a sticky that details the basics. For the most parts, it's the amps on the +12V rail(s) that's most important. Remember, volts*amps=watts.