It's a 7950 on discount for £200 because it has a missing adapter, or possibly a slightly beaten up box. Normally these would cost around £250. Is it worth the extra £30 to spend? I want to max BF3 at 60+ fps, and as far as I'm aware a 660 can do this, but would the improvement be so great? I've been looking at various benchmarks but they're conflicting a little because of driver updates, etc.
7950 vs the 660, the 7950 is the way to go. If you plan on playing bf3 like you said then the AMD cards are finally as good or better than nVidia at running the game lately. Also, most 7950s will overclock pretty well so that is another plus because of the cooler on the one you have. Sapphire is a brand I trust with ati/amd cards too, have a 4870 and 6950 from them with their special cooling on each and they havn't given me any issues.