Welcome to the rabbit hole Dayton! It’s an expensive ride but a darn fun one. As far as power goes, you won’t have any problem with the Sprout100 driving the Polks, or future speakers in this relative price range. Any more or less power with amps doesn’t relate at all to volume/how much you have to turn up the volume knob. How loud it gets has more to do with the gain structure of the amp. I wouldn’t worry about this though because the Sprout100 can drive pretty much any speaker out there louder than anyone needs.
The Sprout over your existing Denon is going to be a much more rich experience. The detail will certainly be there, but what you’ll get more of is that believable sound. The sound staging will become much more apparent and the size of the sound coming from the speakers will be bigger. It won’t seem like the music is confined to and being produced by the speakers.
Sure the Sprout might be entry level in relative terms, but it is one heck of a big jump into achieving the audiophile sound.