futureproof - pfff, like anything is with computers
but as said, if your going to buy 2 7950's off the bat you might as well buy an 8 series card. you'll be happier with it in the long run.
for a power supply, something like this
would be a good idea because it already has the 6 pin harnesses for the video card. otherwise you have to use molex to 6 pin which isn't the greatest, this is actually the psu I'm thinking about getting, i just picked up a cheap 550 from work, but it won't cut it if i end up with another card.