Not for 55+, but for 50 inch, I could say (Panasonic Viera plasma anyway) TH-50PZ700U 50" 1080p (price is much cheaper --> $2.25k, from 55+ it gets much more expensive than it would normally be for more inches on the screen) or for 55+
Panasonic TH-58PZ750U 58" 1080p plasma HDTV --> $3.68k
The image is excellent. They all say Pioneer plasmas are slightly better, but usually $1-2k more expensive, it depends on the budget you wanna spend for this. For large screens, plasma is much better than LCD.
If you wanna use a link, use these:
Panasonic TH-58PZ750U 58" 1080p plasma HDTV
Panasonic TH-50PZ700U 50" 1080p Plasma HDTV