I don't think your Denon would come anywhere close to a B&K amp. Definitely would hold onto that amp. If anything I'd upgrade the sub. I almost bought KEF Q300s and PSB Image B6s before settling on my Totems. Best speaker I've heard for music. Incredible detail and imaging that always makes me say "wow."
FWIW I auditioned both the Q100 and Q300 and kept the Q100. When played with a (good, accurate) sub I heard no advantages to the Q300.
To my ears ... compared to many (also excellent) speakers in their price range the KEF Q series have stand-out off-axis response and an uncommonly wide sound stage (maybe it's the concentric driver?). My listening space is wider than it is deep so this worked for me.