Best card for around $300?

I have maby a max of $320-350 for a new graphics card. I had Crossfire hd 6850's and after a *** load of attempts to fix their problem of no FPS increase compared to one card, i have up and re-installed my old GTX 560ti and it have me a decent FPS increase. I would expect the 6850's to preform much better but they didn't. In PlanetSide 2 for example, i would get 25-35 FPS with the 6850's running both at 98% activity (no bottleneck then) but the single 560ti 1gb would run at 40+ fps at same settings! I thought perhaps i was gettings memory bottleneck since the cards mirrior Vram in crossfire and SLI but yet why would the singe 560ti 1gb run better when it's at same memory? reguardless, i wanted to get a single card with 2gb of memory or more rather than risking another failed crossfire SLI with the 560ti, or, if you're SURE SLI'ing the 560ti wouldn't be *** no improvements like the 6850's then tell me but i don't know if i want to take that chance.

Make sure you recommend a card that will sit well with the rest of my computer:
1. AMD Vishera 6 core @ 4.2 GHz
2. 8gb ddr3 1600mhz
3. 64bit windows 7
4. Decent motherboard with 16x PCI and 8x PCI no 4x don't worry

Thanks in advance!