Probably will have other disagree with me, however:
Blu-Ray should have better sound quality. But, my question would be is how old is your sound system. Best Buy has the best on display, and positioned by professionals to make it sound great. Like having a bottled water stand in the desert.
My Denon 7Ch does much better then my Harmon Kardon 5.1.
I don’t have any sound system - he showed us the Definitive Technology Procinema 60 5.1 with a Denon 525W 7.1 receiver. It sounded great but I have no clue about these kinds of things and began to wonder if I was going to lose the great sound by having a regular DVD player. The whole setup with a Denon Ipod Dock is going to be about $1300.