Well I know you are cutting a lot of corners it sounds like. I did everything from the ground up using an old Bad Dudes cabinet. I got all of my parts from Happ Controls (
www.happcontrols.com/). My monitor is an arcade monitor wired to a vga adapter so it's running at the same refresh rate as an arcade cabinet would. There is no shell on the monitor so all the guts stick out and it's kinda dangerous if you touch the wrong spot I found out once...OUCH!
Coin doors when I built it were wired into the JAMMA harness using a JPAC (
www.ultimarc.com/jpac.html). Then I custom built my controller using parts from HAPP and plexi glass so I could put my own custom graphics under it. However as of 2 x-mases ago I upgraded and ditched the whole JAMMA rig for a Dual X-Arcade (USB). I highly advise you use this if you get a cabinet that will fit it. Lucky me it fit perfectly into the control board area. 100% fit. (
www.xgaming.com/store/arcade-joysticks-a...rcade-dual-joystick/) compatible with Mac. Also I didn't have to program anything in MAME it all just worked like a dream.
I was going to go Mac over 7 years ago when I built this thing but at the time Mac Mame in my opinion sucked next to a PC in performance. Now it might be a bit different but even on my G5 and Macbook it can't compete with the PC I have in there. Plus I can force refresh rates with my vid card better on the PC for some reason.
The inside of mine now only has a motherboard mounted to a bracket on the base. An HD mounted next to it and a USB Wi-Fi card. I custom rigged a power supply to run off of switches I ran to the front of the cabinet to power on the computer and reset it. You could easily get a pc bare bones kit 2 years or older for under 200 bucks and be done with the computer. I know we all love our Mac's and I only use them for everything BUT my MAME cabinet. Oh I did have to do one thing. The speaker in the top back of the cabinet over the monitor was bad. I had to rewire it so I used a Pioneer 6x9 car speaker it looks like it's part of the cabinet and man is it LOUD! Considering all the games I play were designed for one speaker this puppy rocks!
As far as finding a cabinet I found 2 on ebay from a local seller I spent $80 bucks one was my Bad Dudes and the other was a Space Invaders. I went with the Bad Dudes and made a quick $50 on the Space Invaders. Try craigslist as well. Look for local auctions you might be able to find an old machine for cheap that you can gut or use the parts.
If you want pictures or anything I'd be happy to send them along just send me a PM.