I'd take a 7950 for ~$200 over a 760 for ~$250 even though I generally prefer nvidia, but that's just me. It's a personal preference thing I think. Both cards sort of trade places depending on which game you play, with the 760 faster for some (most, I think) and the 7950 faster for others but both offering pretty much the same experience within a couple of fps from what I am reading. The 7950 uses more power and creates more heat. For me though the price is still a bigger factor, unless PhysX or SLI or other factors matter to you.
I'd stay with the 8 gigs of ram for now too personally because I haven't played any games that use that many right now. You can always buy a second stick later, though be aware that new models come out all the time and old models get dumped, so in a year or two you may not be able to find a second matching stick.
ETA: on the other hand, some 760 cards I am seeing on newegg are offering free copies of Assassin's Creed 4 AND the new splinter cell game for free, which seems to be a pretty rockin' deal as both are still $60 games I believe. So maybe that swings the price factor back in the 760's favor.