I have seen several builds in these forums for 600-650.00 that will run most of whats out there on high settings. Now thats pretty much the box cost and doesn't include monitor, keyboard, mouse and OS. If you step up to the 800-900 range you can build something that is still not high end, but will run whatever you can throw at it on ultra settings and be upgradable while holding its own for a few years down the road. Again, though, excluding the peripherals. Thats still not something that would pull off a 3 monitor set up. Thats going to cost you in the gpu department.