sounds like your pretty much finished then, heh heh.
here's some budget conscious parts i've come across:
i know a place here in town that you can get an adequate comp for about $20-$45(200-500mhz) iirc. they also have cheap monitors, $20-$40(14"-17"), could get you by until you get a nicer one. on a side note, i'm heading to stl tomorrow to pick up a pixel touch 21" vga, with tax they run $85 i believe. i could pick one up for ya. i know 85 bucks is nothing to sneeze at, but it's a good deal on a 21 incher.
you could use x-arcade joys and buttons, $20 will populate your cp. i've used the buttons and they work fine. i've heard the joys are ok, if not spectacular. you could also buy the buttons seperate($10 for 20) and pick up some wico joys for $7.00 each or they have 4/8 ways for something like $10.
i've got some leather texture t-molding i'd sell ya for what i paid, or you could go to t-molding.com and buy direct. best prices on molding i've found.
to do the bezel right you'll have to fabricate it. i'd have no problem helping you here. once you've got it cut, slap a piece of smoked plex over the top and it will look great(regal plastics, cut to size for about $20).
i'm not sure if you've got an encoder yet. if not i'd recommend a keywiz. you could also hack a game pad and do it on the cheap. i also know there is a $10, very basic encoder out there. coveat emptor on that one. some guys have had good results with it, others have not.
you could at least get the cab up and running for a bit over $100. newer games would probably have a tough time on this system, but all the classics should run fine.
just throwing out some ideas.