I used a ATI All-In-Wonder Pro in my MAME cab with the original 19" (standard arcade) monitor. It can't handle the resolution for all of the games, but enough of them for me to be satisfied with (somewhere around 500).
If you're seriously interested in building a MAME cab I'd recommend you check out the ArcadeOS and Ultimarc/J-Pac message boards and see what those guys are using.
watch out, he'll come back as yoshi X, yoshi of the future
and he'll joyousley exclaim how the thrashing due to lack of social skills he recieved on this board shaped him into the only man capable of repealing an alien invasion by the zentradi 2 decades from now
I guess I am pretty serious about it, it's almost done!
Just need the right TV (20", s-vid and scart, flatscreen.. just looking for the exact right thing to finish it).
It looks nice if I do say so myself, black and white scheme. Two white doors at the front to access the consoles, basic black cab,white control panel with black buttons, white edging round the sides and a (prodominantly) white Gradius marquee.
My cab has a bid swing door on the side for easy access to the rear of the monitor, computer parts, and anything else I decide to put into it, I should post my design, it looks sorta like the mortal kombat 2 cabinet, but much more neato. I need to paint the bugger still. I woudl like to make a stencil of something and just spray it, back to the basics!