One of the hardest things I found when TV shopping is that you can go look at them, but they're usually not set up well, they are often getting horrible feeds, the lighting in the store is nothing like what you'll have at home, and the salespeople often provide you with more mis-information than anything else.
I went with a LCD RPTV because I wanted a significantly larger display than you're looking for and a flat panel was no where near my budget. I have less than total light control in the room so I couldn't go front projector. This left me with dlp and lcd rptv. I preferred the lcd from my trips to the retail stores.
Since you have stated that you really want a narrow television, I think you're right, this narrows down your choice to LCD or plasma (note my LCD-RPTV is only 20" deep, but it's quite big relative to an LCD panel or plasma).
I think the next thing you need to do is decide on a ballpark price. $2k, $4k, $6k? LCD is more money than plasma for the same size, so the budget could come into play. EDTV plasmas are a lot cheaper than HDTV plasmas. For me personally, getting HDTV was important, and I just couldn't buy an EDTV and down-convert HD.
I think they are very helpful at avs, a lot of the posters are very technical and extremely nit-picky. This can be helpful, but sometimes when they say something is "awful" it's only noticeable side by side with the best competitor, and hardly noticeable in normal settings.