if you plan to go the windows route, I would strongly consider going SVid instead of an arcade monitor if you don't one one already.
http://www.xiaou2.homestead.com/turbo.htmlthis is a great show of the difference between a SVid tv and a SVGA. I'm not sure how much better the arcade monitor is. (anyone with both setup's and a digital camera willing to do some closeups?)
But the TV-out route will help the setup considerably and allow you to run windows applications/emulators. There are only super old video cards that can handle the windows on an arcade monitor (g200 I think is the best right?)
I'm going arcade monitor next probably, but because I have a working 19". If I didn't own it, I would definately go SVid