totem/nad denon

If you enjoy listening to music, you are definitely going to hear a difference. The NAD and Totem are a great combination for a 2 channel setup. For starters, Totem speakers need high power and current which the NAD has.

It’s a matter of priorities; the Denon/Totem system will sound different for listening to music, but you’ll gain a HT setup. What is the Gallo system for?

I’m not sure, but you may be able to keep the NAD as your amp and hook up the Denon to the NAD’s Tape Loop and have it pass thru the amp for HT purposes.
 Somebody on the forum with more HT experience can probably advise if this is possible.

I am with Lowrider in that i could not see replacing a 2-channel NAD integrated for a HT receiver for music. That said, you should try both and answer the question for yourself. It is possible that the sonic difference may be overshadowed by your other considerations. 

I've had Totem ARROS with the predecessor NAD C370 integrated in a prior "B" system, so I do have hands-on insight into the performance characteristics of the two together ( and not just some anecdotal I read it in a prior post re-hash)

Simply put, the  DENON receiver (in fact,  just about any receiver other than the $6K ARCAM ....) ) will be a step down from the NAD integrated amp with your TOTEM speakers.

With the exception of the top ARCAM and perhaps a minuscule smattering,  receivers are cheaply built-to-the-lowest-price point possible  kit (usually chi-fi ....) that lack the quality build power  supplies  and high-current amps to generate the high current output necessary to drive the grunt-hungry Totems. WPC stats in isolation to the above are meaningless .

The difference(s) in performance and quality stepping down from the NAD integrated to the receiver will be noticeable and those differences will not be subtle.