and no, I'm not gonna build one. No.
Are you sure? It really isn't that hard to do so. If your not comfortable doing so you could instead hire someone else to build it for you. This video has a ~$500 computer that can play bf3 with 1080p 60 frames a second on low settings and Black Ops 2 at 1080p with 60 fps at highest settings. It also has easy to understand step by step instructions for building the computer.
http://www.youtube.com/watch?v=Bh455l3348s
If however you are set against building/commisioning someone else to build for you a custom computer, the only advice I can give you is to pay attention to benchmarks like www.cpubenchmark.net to get some idea of what kind of performance you can expect to get and don't buy an alien ware computer; they are horribly overpriced.