Akg_ca: I would suggest getting an ISF certified calibrator. THX is a rather ridiculous specification as it's also a label that any manufacturer can throw on a product if it's even remotely capable. I've had all of my televisions calibrated by an independent IHF-certified technician and couldn't be happier with the results. It's real science, and not questionable at all.
Sorry to go OT. Plasma TVs historically run hot, there's no denying that. The originals used fans for cooling, but were too noisy. When they stopped using fans and tried convective cooling, the displays had less life, and the circuits suffered from potential heat damage and component lifting in some cases. Plasma TVs have been considered the best-performing displays in terms of black level and color reproduction. I would argue, however, that modern LED sets are approaching plasma TVs in performance. My calibrator told me that my Samsung LED had the best black levels he's seen outside of a plasma, and it was very close. LEDs are slim, cool, and preform very well.
The only potential drawback would be the back light. In a dark room, when a passage in a film goes black, you can see faint white light in some areas of the screen due to the edge light.
Two cents.