Improvement over 2002 Denon AVR-3802 for 2 Channel Music System

I currently have a 2002 Denon AVR-3802 that I am using for a dedicated 2 channel audio system.  My room is a converted garage bay, about 15'x24' (with a bunch of guitars and amps and such in it - multi purpose room...)  I have Revel Performa3 M106 stand mounted speakers, and an SVS 3000 Micro sub.  I am streaming using Roon (Qobuz and Tidal as well as DSD "rips" of my SACD collection) into a Ropieee loaded Raspberry Pi 4 into a Geshelli Labs JNOG2 (with AK4493).  I have a Sony BDPS-5100 for playing CDs via coaxial out into the Geshelli (also used for ripping SACDs).  For vinyl. I am using a late '70s JVC QL-A7 with an AT VM540ML cartridge into a Schiit Mani2 pre.

Anyway, overall the sound is really good.  However, I am being tempted by the idea of separates, and what I can do to best improve my experience.  I am thinking middle-of-the-road for now.  No Mark Levinson or Mac (yet).  Candidates include the Parasound P6 pre with either the A21+ or the A23+ power amp, or maybe the Anthem MCA 255 Gen 2 (not going to go all the way to the Anthem STR).  Another extremely interesting idea is the Benchmark AHB2.  For budgetary purposes, I would likely buy an amp first, and continue to use the Denon as a pre for the time being.  I use it in Direct mode, WITH bass management (speakers set to small - sub set to on). Eventually, I would want a pre with Bass Management as well.  Not super interested in a pre with a built-in DAC, but most seem to have this (Including the P6).  After that, a better phono stage...

My quandary is, what will I really gain here with a new amp?  The amp section of the Denon is solid- does not seem to be lacking much other than lower volume push / punch / control and (of course) definition at more extreme SPLs.  I feel like the A21+ would be a significant improvement, but not sure I want to drop $3k on an amp when the current situation is pretty good. 

I guess I am wondering if a lower wattage (closer to that of the Denon's 105 WPC), lower $ amp (like the A23+ for example) will get me any significant (audible) benefits over what I have, or do I need to bite the bullet and go with the A21+ or Anthem.  I know that eventually the Denon will give up the ghost, but I bought it brand new in 2002 and it has never failed me yet.  I just want to get ahead of its inevitable demise.  I know it seems like I am answering my own questions here, but I think I need some affirmation from like-minded folks. 

I'd hate to drop a few grand and be nonplussed with the results.  Not a unique situation, I know. 

Talk me into it.