J-Pod is right — decide on what size you need and how much you are willing to spend. The rest is too confusing, especially if you add DLP TVs into the mix. DLP is digital light processing, and offers you a cheaper (but not flat) alternative — they are more like the older big projection TVs, but not nearly as deep or heavy.
The real point is, get thee to high-definition anon! High-def totally changes the TV experience, especially with sports, nature programs, and movies. (It doesn’t do much for sitcoms, except for occasionally show part of the set you shouldn’t have seen — the widescreen 16:9 aspect ratio still confuses some directors and cameramen!)