My 90W/channel Denon from a few years ago has no issues whatsoever. Companies don't usually change a design that "works" so I doubt very much that this higher end Denon amp can't drive the 80s.

I'll bet that whoever you were talking with at Denon simply goes by the spec in the book and has no practical experience in this area. Try to get to someone who has deep knowledge.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated