I would think you should be able to pull at least medium settings with that rig at 720p. The reason you could not max it is because your CPU will bottleneck at that resolution. This is caused by the "mesh quality" graphics setting, which determines how far you can see spotted enemies. Plus, the lower the resolution, the more stress put on the CPU. The Phenom line is extremely solid, but games are beginning to catch up with it. However, in servers with lower player count, like 24 man or 32 man, mesh quality should not be an issue.