I have one of these cabinets that I converted to a MAME cabinet using a television for the monitor. If I remember correctly, the inside width from end-to-end is something like 23 and a half inches or so in the cabinet, more than sufficient for a 19 or 20" television but very little else. This is a very narrow cabinet really, ideal for vertical monitors or 19" horizontals.
I've looked at 25" tv's for the cabinet but all of them are too wide. I've bought an Apex flat-screen 20" TV that gave me a few more inches that looks awesome, and I've considered simply rotating this TV on it's side so at least vertical games could be played with very adequate height (I've experimented with having the TV on its side for days and days and have had no problems). But a 19" TV, horizontally placed, looks great too.