Why rush to LCD?
These days, its possible to convert ("mod") almost any old CRT TV into an arcade "monitor" for a cab, with either RGB or component (DVD) inputs. True, that might involve a little soldering, but is all easier than you might think. Then you just setup Groovymame with a compatible video card (cheaper than you might think!).
This would be a significant improvement from the s-video, direct out of video card, that you had before (that would have been all 640x480i I think).
If you choose to take the CRT route I promise to help you / advise for any modding required
If you can find an appropriately sized CRT TV with
component/DVD inputs then
no modding required, I can sell you a GreenAntz transcoder (cheaper than you might think!) and you just plug it in to get going.