By "LCD projection screens", do you mean LCD rear projectors or LCD flat panels?
If you're considering rear-projectors of any sort, then definitely go have a look at the DLP rear projectors. They seem to have much better black levels than any LCD or plasma technologies. The trade-off, as with any rear projector, is that you don't get the same view when you're off-axis. Performance also degrades when the ambient light increases, but this issue applies to just about everything. Recent RPTVs seem to be adopting anti-glare screens, which can help noticably. All plasmas, as far as I've ever seen, suffer awful glare problems.
Large LCD flat panels are the new kids on the block. As we
discussed recently, you pay more than a plasma of the same size and you don't get quite the same black levels. However, you get much better performance in a room with lots of ambient light.
Burn-in on plasmas is a big issue. Burn-in is a non-issue on DLP or LCD technologies, as far as I know. Since I insist on watching 4:3 TV in a non-stretched mode, that means I'm often looking at vertical grey bars on my (CRT-based rear projection) TV. For now, I haven't seen any signs of burn-in. When you see plasmas in the airport with flight information on them, you always see signs of burn-in.
If after all of that you still want a plasma but you don't want the cheesy speakers, you might investigate the "professional" lines offered by several manufacturers. They often have the same exact glass, but minimal bezels, as they're intended for industrial applications like the aforementioned airport monitors.
(Oh, and my dad also has an inexplicable desire to buy a big, expensive flat panel TV and use the cheesy built-in speakers. The mind boggles.)