Upgrading my 7970 @ 1080p/Eyefinity

First off, I have a fx6300 and a 650w EVGA powersupply. No SLI/crossfire support on my board.

What are the best options for $250?

I see a Zotac 970 on Jet for $250, or I can get a 390 for $280 but this would be absolutely stretching it unless the performance gain is amazing.

Another option is a 780 which I can get for $200. Worth it? Or should I upgrade my cpu/mobo?