That Rotel amp can drive your speakers to well over 105 dB for sure. Reference level is 105 dB peak and that is too loud for most people. The Rotel is not going to do anything for two channel listening because your Denon avr can also drive your speakers to reference level from 10 ft. It is true that reviewers often would say you need more power to "open" speakers up, that could true in some cases, but in many cases, those were just bs, or hedging. They might say that so if you bought the speakers, don't like them, they could say, I don't you these speakers need more power to sound good. It's almost silly, and sad for such bs to flood the internet, but it is what it is, people just have to do their own research before spending big money on amps that they may not need. You are doing the smart thing to do your research before making a decision on this purchase. Mind you, in most cases, it is better to have power you don't need than power you need but don't have.
You will likely get the "wow" you are looking for by going with better quality contents than Apple music and using the TV output to feed the Denon.
Also, many people will say better DACs with better specs on paper, won't make audible difference, but in this case, a good source (high quality recording content) with a <$150 (even <$100) DAC such as those from SMSL or Toppings using analog input to the Denon and listen in direct mode would likely make a difference too.
If that doesn't do it, then I would say replace those speakers. @AcuDefTechGuy
, who used to like his Def Tech speakers (that's long time ago, he moved on since...) may be able to give you a better idea on whether those Def Tech 7004 can benefit from that 500 W rated Rotel RB-1092.