Picking the right HDTV is no cake walk. Years ago there were educated salesmen (and women) who could guide you through what set was best for you. Today, Blue Shirts at Best Buy and the woman checking you out at Wal-Mart respectfully don't know squat about the difference between 1080p video and UltraHD. They don't know how to advise you on if an LCD/LED set is better for your room than a plasma. They don't know how far to sit from the set. They don't know how high to mount the set. It's a mess.
Picking the right HDTV for you isn't as bad as it sounds. First is focus on the room that you are working on. Is the room able to get dark or is there a good amount of ambient light? If you've got ambient light most of the day – look to an LED over a plasma. Today's plasma HDTVs still make the best black levels which make for an "inky" picture that videophiles love but LED's brightness helps overcome the setbacks that afternoon sub brings to your room.
Have you ever considered using a front video projector and screen? If so, there are affordable screen materials that are "negative gain" that reject light thus can be used in almost broad daylight. Even with an affordable ($1,000) projector – you can pair a neg-gain screen with cheap projector and get a HUGE image for a $3,000-ish investment. Considering a 100 inch plasma cost about $75,000 – that's one hell of a bargain.
The last tip is the best: HIRE a professional THX calibrator. HDTVs come out of the box designed to look good under the God-awful sodium lights in a warehouse store. Getting your HDTV to SMPTE standards will not only improve the image by 20 to 30% but it will make your set last longer.