Chess has covered much already; I will just add a couple of points...
-Would QS4s as rears be superior to conventional bookshelves in an asymetrical set up (hybrid tweeters vs 1" tweeters).
Regardless of the tweeter driver, the QS surrounds (thanks to its quad-pole configuration) are more forgiving on less-than-ideal placements than directs.
-How seriously should I take the Denon manuals suggestion to not place speakers further than 16' away?
I have no idea why Denon specifically recommends that way. I wouldn't care anyway.
-Can the non-ported VP100 be used as a rear surround? side surround? (that would be ideal due to room constrictions - one on top of the mantle and the other under the overhanging bar in the kitchen).
You can certainly do that, but as the side surrounds, I believe that the QS's will do better job in general, especially in reproducing ambience.
