Well I could probably spare a max of $500. What Mobo would you recommend? Or would upgrading from the 7850 really be the better option? I feel like next gen cards will be coming out "soon" so I should hold off for those.
I agree that a GTX770 would be a nice upgrade. Your CPU is powerful enough for any game. You might also get a $20 Xigmatek Gaia (cools within 1C of the more commonly mentioned Hyper 212 EVO for 2/3 of the price) and overclock it some. Still, the graphics card upgrade will make the biggest difference.
Another 8GB is unlikely to make any visible difference, at least not in games. Crossfire remains broken, so I don't think it is a good idea. If you prefer to remain with an AMD card, get a single HD7970.