I would go with the 7950 if at all possible. The 7870 you listed is nice, but it's over priced as far as I'm concerned. If I wanted to save a little and have close to 7950 performance levels, I would get:
Well always get the faster card if you can afford it... Still, the card lunyone linked is a good bet, since you can't make your mind and that card is basically the middle ground between them. You'll have to overclock it manually though, which is always good advice for anyone.