So you want to buy a card for six or eight weeks of play? Check HERE
for the current best, but the next generation is just around the corner, possibly as early as October, so you need to decide if you want to buy the best now or should wait a short time.
I would just buy a 760 now, or perhaps a pair in SLI, and then spend some cash when the next thing is here.
Sure, two cards produce more heat than one, but you get significant performance.
Your budget is good but you may not want to spend it all now.