I would suggest cutting down on the power supply a little (there is barely room for 650W worth of hardware in a mITX build anyway), and getting a better SSD. The Vertex 2 is outdated and infamous for its poor reliability.
The rig would do okay-ish in BF3 etc., but a faster graphics card wouldn't hurt. Depends on how much you can spend though.
What would be a better card for under $200?