More than anything else, I think the superb PQ you get from using the Sony player instead of A2 upscaling comes from the outstanding internal upscaler of your TV.
For my 42PV70, I use a basic LG DVD player (hacked to region-free) that I bought at S&R for P1900+ when watching SDVDs and PDVDs. The Panny's internal Vreal2 upscaler does a great job of upscaling the LG's 480p output to 720p / 1080i. I exclusively use my A2 for watching HD-DVD videos (and not for upscaling) on the same TV.