I've been working in the television industry for over 15 years. Recently I was at a seminar on signal quality with some of my colleagues. We got into part of the discussion regarding HDTV and what is the best signal quality you can get at home. And honestly, what people are getting delivered to their homes as HDTV is not necessarily a 1080i or 1080p image. At least via home satellite and cable systems. Both cable systems and Direct TV are digitally compressing those HD signals for the purpose of transmission. They're not devoting anywhere near the true ammount of bandwidth that those signals require for 1:1 transmission.
Where can you get a true HDTV signal? A few places. Most of the next gen gaming platforms have HDMI outputs. And then there are the HDTV ready DVD players, regardless of which format they're using. And finally there is over the air transmission from local stations. Believe it or not you can get a true Hi-Def picture at home just by hooking up an antenna for the over the air stations. And transmission of those signals is now digital, so you won't have hash in the image if you don't have good reception. Either the signal is solid or it might go to digital blocking or black if the signal quality is poor.
As for the sets themselves? Plasmas have been marketed as the top of the line, but that's not necessarily the case. LCD's are almost as good. But I've heard the most promising things about the DLP sets. HOWEVER, you may also want to look at a CRT set. The image quality is amazing. CRT's are very tried and true and that's what is being used in the television industry for video quality control. They're not as compact as the flatscreen televisions, but I think you may like the image quality. Especially when it comes to viewing the set from different angles in a room.