I find this rather coincidental that your impression of sonic quality increases with price and model size.

Oh right, that bias thing again.

Try an A/B instantaneous switch the next time you set this up. It will help remove that bias.
I've done this with the VP100 and 150. I challenge anyone to try and hear the difference between those two in a complete 5.1 setup.
Subtle is not even close to describing how minor the differences are.

"Those who preach the myths of audio are ignorant of truth."