My old set (2010 TC-P50G25) did have the THX mode, however, I never really used it after playing with it a little after purchase. I found THX to be far too dim for my taste and viewing environment. I ended up using the aging slides for the full 100 hours and plugging in the D-Nice settings for that TV at the time. I was pleased with the picture, but never wowed by it. The new panel (2013 TC-P50ST60) is much nicer than the old in overall picture quality (black level specifically is noticeable better), functionality and frame design. I never liked the shape and amount of frame on the 2010 TC-P50G25. There was too much frame and the “lip” at the bottom was ugly. The 2013 TC-P50ST60 has a much nicer minimalist frame design if that matters to you.
The 2010 TC-P50G25 just died one day when I shut it off. There was an audible pop much louder than normal and the red light was blinking four times. After a power cycle disconnect/reconnect of all cords the red light was blinking ten times. The panel was babied. It was hung on the wall and never touched after initial setup. I sure thought (and hoped!) it would last a lot longer than 3.5 years, but what can you do? The 2013 TC-P50ST60 was available at a great price and I was happy to upgrade anyway. FWIW, I do still have a 2006 Panasonic TH-50PHD8UK (commercial panel) in use in my house and it looks as great as the day I bought it, though not as good as the 2013 TC-P50ST60.
thank you for the response.