smeezekitty :
The 7750 does not need a power connector. XFX makes good lower end AMD cards.
I wouldn't say twice the performance. Probably more like 50-70% faster.
The Radeon HD 6670 DDR 3 has 74% of the performance of the Radeon HD 6670 DDR5. The Radeon HD 7750 / HD 6770 / HD 5770 all have the same performance and is on average 40% faster than the Radeon HD 6670 DDR5.
Radeon HD 6670 DDR3 = 74%
Radeon HD 6670 DDR5 = 100%
Radeon HD 7750 DDR5 = 140%
Another way to look at it:
Radeon HD 6670 DDR3 = 74 FPS
Radeon HD 6670 DDR5 = 100 FPS
Radeon HD 7750 DDR5 = 140 FPS