6750 ($95) vs 7770($130)

Hazle

Distinguished
could've sworn the 6750, like the 6770 was a re-branding of the 5750 and the 5770 with added features that were exclusive for the HD 6000 series.

either way, the 7770 performs slightly better than the 6770 at least in some benchmarks, even more so at 1080p compared to the 6770. it's slightly more efficient so that may help reduce the amount of power you need for your PSU.

i'd be willing to spend that extra $35 dollars if gaming is a major use for your PC.