You can't bypass the Denon unless you run Y connectors from your inputs to both pieces and a second set of speaker wire out to the speakers from the integrated amp. If you do that, make damn sure the Denon and the integrated are NOT both powered up simultaneously.
You could then do an A/B comparison by alternating between the receiver and the integrated but I'd wait a few minutes after powering one down before firing up the other.
You could then do an A/B comparison by alternating between the receiver and the integrated but I'd wait a few minutes after powering one down before firing up the other.