OK time to upgrade the 10 year old tv I have currently

I am a simple guy and want to keep my options open to a few things.

Projector is out for now

So what I need to be able to do is:

Have HD capable tv but still get a decent quality image from normal cable and dvds.

I am looking at plasmas right now but is my expectation even realistic, because the image I have seen so far is shit on normal signal.