I upgraded my 2011 machine with a new nvidia card, and 8 GB memory that the community helped me pick out, so I have the Radeon and 2x2GB of RAM if anyone has a use for them. On my machine, at least, I was able to get between 22-30 FPS with the default settings.
GIGABYTE Radeon HD 5770 DirectX 11 GV-R577UD-1GD 1GB 128-Bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFireX Support Video Card
Mushkin Enhanced Redline 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model 996805
