I recommend the Panasonic TH-42PD50U 42" Diagonal Viera Plasma EDTV - it will give you best viewing on regular non-HDTV and DVDs/Tivo....and it still does a fair job of down scaling HD source. It has an HDMI input aswell, which may become standard in the future....
Colour and contrast is impressive and signifcantly better than other TV's, LCD or Plasma or rear projection, in that price range....best value I have seen...no wonder it is one of the most popular TV's last year and this year.
Currently available full HDTV Plasma/LCDs with all the pixels necessary to display full 1080 HD signal are very expensive and any scaling of source pixels to screen pixels (up or down) is best avoided and, worse, some HD sources are 720p as well as 1080 to complicate it all further for screens with fixed pixels. If you want best quality for all sources then the 5 year old CRT Sony 36XBR400, which was top of the line at the time, still does a great job without scaling problems but it is a heavy beast and will not like speaker magnets getting to close - but you might be able to find one second hand at a good price...