Don't spend 350 on another 6950, they weren't that much new. If you can't find one for under $200 then you 350 is best spent on a 7970. Or better yet, sell your 6950 in Brazil (sounds like you'll get more for it), and buy two cards with the extra money here (not sure how much you'll end up with).
The 650W will be fine.
Look at the "Best SSD for the Money" on this site for recommendations based on your budget.