Plasma vs LCD , Plasma has like ~500hz refresh rate while a typical plasma at your price ranger has 60-120. This means , especially if you watch fast action scenes or sports*** , when things zip across the screen, you can actually see it in detail without either it bluring or leaving a ghost trail.
I would probably go with an LED LCD in your price range, and choose a badass super high end plasma if you had more money
as far as the quality of the TV first, make sure you have the correct signal coming in, and correct signal being sent out to the TV.
One thing I tell people is that a home theater, in today's time with today's technology, is made more from the sound you have and less from the visuals. This means sometimes people spend all their money on the TV and forget about speakers. Some nice 5.1, 7.1 + REALLY adds to the experience. Something blows up in the movie you watching? FEEL the explosion with the thunderous bass... Something ZIPS from left to right in the movie? HEAR it in real life.
Just something to think about. If I was you, which you are already doing, I wouldn't spend too much money on a TV right now. (I mean like ~700 vs 3,000) -- Reason is, i reckon by the end of this year or around next year, TV technology is going to REALLY be kicked up a notch