DO not SLI! It is not worth it with it unless you want to game on 3 monitors. Plan to game with 1 GPU. 2 GPUs causes microstuttering which is annoying when gaming. You're better off with 1 GPU. If you need to upgrade then sell your old one and get a new one.
8320 is great. Overclock it with a Cooler Master Evo. What's your mobo?