How well do non-nvidia cards work out with AMFP?

[Ashtoreth]

When AMFP came out, I played it on a computer with a Radeon HD 6950 and 8 GB of RAM, and the game ran perfectly on the highest settings with a resolution of 1920x1080, although the processor was more powerful than yours (AMD FX 8-Core 8350).
Anyway, you shouldn't have any problem at all.
Even my PC, with an AMD Athlon II X4 635 + Radeon HD 4200 + 4 GB of RAM, is able to run the game (on low settings of course XD).