The 7850 2GB is the best option, brings good performance at even high resolutions and the extra gigabyte of memory allows you to crank up Anti-Aliasing and details without running out of memory and getting large drops in frame rate like I used to get with Battlefield 3 and Skyrim on my old GTX 560 1GB (used to run out of VRAM).
The GTX 650 Ti 1 GB (non boost variant) is supposed to drop to $130 in the US due to the Boost's release. Otherwise, in the AMD camp you'd be looking at a HD 7770. That will be around $130 too. The 650 Ti 1 GB will beat the 7770 though.