Well my Video source are kinda crazy, we have Dish, Directv, and Charter. Best PQ for SD is Charter and I tend to watch it more due to ondemand. I had a 50" vizio plasma which made the SD PQ on Charter look amazing but the TV died about 13 months after purchase and since getting the LCD The PQ is just really bad in SD, blurry text pixelation allot etc. HD is fine, its really the SD Im trying to improve.

My equipment sources are:
Direct HR22 - HDMI
Dish 722k - HDMI
Motorolla HD DVR - HDMI