I think you nailed the issue here. Try some BluRay HD player and see if it looks better.
Ideally We want a better picture without going to HD cable service. Do plasma screens get fuzzy/grainy after 10 years of use? We're looking for more clarity in a bright sunny room. Is HD required?
Our current unit is a 2002 Panasonic th42pw5 plasma display with basic Comcast cable service. The screen has served us well for a long time, but I feel like it's lost clarity. Is it only because we now have an HD LCD Sony unit in the other room?