I've got a 32" in mine, and I'm pretty sure I would have been just as happy with a 30". But my 32" fits inside WITH the case still on.
The viewing area based on my seat location is just about perfect. One thing that cabinet design really has over mine is that you can hide everything in that big empty cabinet when an LCD is used. Like on mine the AMP, AMP Power Supply and power strip all ended up on the back of the main cabinet, and the computer off to the side (on the floor for now).
If I cut a bigger hole in the back of the cabinet, and de-cased the PC, I could probably get everything inside... something I'll have to think more about. Might require a little re-engineering of the cabinet supports inside as well.