I think plasma is way too expensive for what you actually get. What I mean by that is, I don't think the technology is where it needs to be right now and it seems that the life of plasmas right now is around 3-5 years. If I spent 6-10k on a plasma and it went out in 3 years I'd be really pissed. One thing I would recommend is to look into a DLP TV. Picture is just as clear as plasma in my opinion and is more reliable.
Also keep in mind that not every channel you watch will be viewed in HD. As of right now Time Warner only has a handful of HD channels. All others will be viewed in digital or regular over the air quality. If you purchase a TV with a built in HD Tuner you will be able to receive all of the local channels in HD over the air, some of which aren't offered by cable/satellite companies.