I spent days on the internet researching that question! I think the 800 has high res audio, and the 700 does not. The 800 is much heavier and larger and gives the outward impression of a more premium unit. That being said, I have had two 800's, one was quirky and skipped/froze often (Geek squad was unable to remedy that situation) so I bought another 800 that has been trouble free. I then added a 700 to a different room and have been equally pleased with that unit as well. My advice would be to go with the cheaper unit unless you have a "state of the art" sound system.