Re: thinking abouting buying a used HDTV...
Don't buy a CRT as a replacement (I assume you were typing that rather than CTR).
DLP and LCD is decent, but each can have it's share of potential issues.
I'd also expect that people are offloading their 720p or 1080i sets for 1080p sets, which may put some decent ones on the market. While there are benefits to having the latest and greatest, I'm on a 42" 1080i dlp, and just bought a 32" 720p lcd.