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

Thanks.  Some great advice - totally get that!  This room is, however - if not "untreatable" it is at the very least "difficult to treat" in its current form.  For me.  I have done what I can , but there are so many things getting in the way of that.  Below is a pic of when I was taking measurements with an old Spectrum analyzer.  It is from directly behind where I put my chair to listen, when the room is in that "mode":  It is a combination practice room, YouTube Studio, and listening room.  I am only afforded this one space for all these endeavors.  It is really tight, and houses a bunch of stuff.  Even more junk is behind the camera...
Music Room Pic

You can see the Revels to the left and right of the guitar amps.  The PA speakers are going to be taken out, so there is probably opportunity for corner bass traps or some other treatment there, but that is the backdrop for my YouTube channel, so not sure what to do, exactly.  Believe it or not, the sound is pretty good in the listening position, and I have EQ'd the sub to the extent I can using the analyzer and the SVS app.  I know it will never be acoustically perfect 
(or even close).

Thanks!  More interested in separates.  I am looking for "old school" - Class AB amp - separate pre / power / phono / DAC.  Not really looking for anything with "big tech" like room correction etc. I want to keep it simple and with the least amount of stuff that requires software updates in the core components.  I work in IT and want to leave the complexity there  - not in my audio chain., if that makes any sense.

Thanks, to all.  The Black Ice stuff looks nice.  I am not big on processing the signal though.  I can only think of aural enhancers like the 'ol BBE Sonic Maximizer...  Not my bag. I realize that this is an antiquated example, but every time I have heard something that purports to fix audio issues using an algorithm or some sort of processing, I am skeptical.  

My Denon, being a 2002 has a MUCH better power section than the AV receivers of today (IMHO).  Anecdotally, I know this as I replaced the 3802 with a 2018 AVR-3500h in my Home Theater system.  The 3500 is ok, but does not have the "authority" that the 3802 had.  Especially with 2 channel content.  TI do know that maybe a more fair comparison would be a 6500 series or something.  But the 3500 was at a similar relative price point to what I paid for the 3802.  That said, the 3802 is getting old.  Also, to many of your points, the Pre in it was never "audiophile grade", but built mostly for AV use.  Totally get that I need to replace it.

To answer some of the above questions, I like separates for serviceability and signal isolation.  I like the idea of "older school" design in most of the components as I do NOT want to be upgrading an entire integrated amp each time technology changes.  I'd much rather have an outboard DAC and Streamer that I can swap out at much less expense and keep the pre and power sections.  Another reason - Budget / Cashflow.  I can better rationalize getting a Power Amp for $2-3k now, a pre for $ 2k 6 months or a year down the road, and then a better phono stage for $1-2k in 18 or 24 months, rather than spending $6-7k all at once.  Replacing my existing components bit-by-bit.  Just a process that makes sense to me.

Thanks. I forgot to mention another amp I am looking at is the Outlaw 2220 Monoblock (pair). Or maybe the Emotiva XPA-2 or the monoblocks (XPA HC-1).  Too many choices...