spend money only on HD (high definition) It will be the only format supported in the near future.
ED is for chumps (no offense intended) who do not do the research.
You will also need a source for the HD signal to really enjoy it. That would mean a HD box from your cable or sattelite company. Or an HD tuner if you live a metro area and can put up with what the networks pump out.
Size and manufacturer are set by your budget. The big box stores like Costco and Sam's have pretty darn good prices. Price compare and check on line.
Remember, sales people push what they sell. That is, if they have a lot of DLP, that is what they will tell you is the best. Know what you want the set for: Plasma if you like movies, DLP if size or sports is your main concern.
Regards,
efxguy