Should I go with the Phenom X4 965 and a 7770 or the A10-5800k with a 6670 in cr

Hello,
I'm looking at putting together a budget gaming PC for around $450, and I've run into this roadblock. I'm wondering whether I'd be getting more power out of a single HD 7770 GHz Edition GPU with a regular CPU vs an HD 6670 in crossfire with the A10-5800k APU.

If I were to go the crossfire route, I'd pick up some really fast memory to bolster the APU, as I believe that would effectively increase its performance.

Neither build would have much room for overclocking, as I plan to use stock cooling.

The two builds I've put together are $9 apart, the build featuring the HD 7770 being the more expensive.