You'll also need to at least borrow a cd-rom drive, and a keyboard / mouse unless you get a trackball. I personally have an actual keyboard and mouse dedicated to my cabinet because it is really more of a hassle to try and do everything with the CP trackball, or hooking/unhooking a keyboard (it will be needed more often than you think..)
As far as the games go, SF4 will probably be the hitch. That's where the most performance is going to be needed. There are some games that don't run well unless you have a very fast processor (I would recommend a 64 bit OS regardless because it gives a decent FPS bump), but those games run like that because they are not properly emulated. Blitz runs very playable on my modest system, as for gauntlet legends and Mace the Dark age? Screw those games. Mace is not a very good fighter, and gauntlet legends is fun.. for a short while, until you find yourself mindlessly pushing the credit button to continue forever. It's actually more fun when real money is at stake. If you really need gauntlet legends, you could get a dreamcast for not a whole lot. It's really more of a "look how fast my PC will run this poorly emulated game" kind of pissing benchmark. If you wait for the emulation to catch up, those games will run on the same "lower end" Pcs.