I called the toll-free number in Canada(for Canada) and talked to tech person who said it does apply logic7 on to 5.1 sources. He said the lower one(520) does not but the 8000 has the processing power. He sounded like he knew what he was talking about. That combined with the earlier thread here I believe it does. There is not much discussion on that receiver anywhere. Even in the flagship receivers board hardly anyone talks about it. In fact, there is about one thread in two weeks over there. It is a nice feature-rich receiver. Either not many buy it because of the bad rep the 7000 earned in its early days or people are so happy they do not have time to visit any of the forums.
About the bass enhance I think it has a mains+sub setting. About the tweakability, I don't think so. I did read the manual a couple of times. I did not see it. If they give full tweakability they will narrow the difference between HK and Lexicon. Right now the Lexiconers can be proud that they have full control over the logic 7 settings. May be in AVR9000?