Do high dollar mono blocks truly improve the Sound Quality over the mid tier amps

Tried to focus the discussion on amp upgrade to folks with direct experience rather than a general system critique. @ghdprentice  thank you for your kind words.  In response to comments on my pre and music server I will offer this.  I have the new Innuos Zenith NG on order arriving in a few weeks.  As to the pre I recently sold my VAC Signature Mk IIa (SE) which was in the system.  I preferred the pre in my MSB Reference DAC which has one additional balanced input that I run my phono pre into.  Room acoustics are great.

@davetheoilguy Thanks for talking about the question I asked and not talking about room acoustics which I did not ask about.  As I said in the OP I love the sound of the Delta amps.  I actually moved from their older model the CT-M600.  When I inserted the Delta's I had an immediate and significant positive improvement in SQ.  That's why I have wondered if there are further improvements to be had. Unfortunately, no one in this thread has responded to my question directly based on direct personal experience with an upgrade.

@aewarren If you would read my OP you would see this " I'd love to hear from folks who have made this move in their systems or heard comparisons at shows or dealers."  I am asking about OTHER PEOPLES experience with a power amp upgrade.  Moreover I'm NOT asking for a critique of my current gear or listening room.

@yyzsantabarbara Thanks for this insight.  My sense is your correct about sound signature of amps as others here have stated.  It seems there are two categories  in sound from the various manufacturers, the detailed airy amps vs the fuller punchier ones.  I'm thinking Constellation vs D'agostino. Plus one pays dearly for fancy casework. The Class D's also offer a viable alternative as @audioman58 suggests.  Low energy consumption and light weight.features are very compelling. 

@wspohn & @verdantaudio , thanks for these observations.  I'm also in the "warm" "musical" camp as I think most are.  I'd maybe describe it as neutral vs colored where "colored" is not a bad thing.  Measurements only tell one side of the story. I find colored amps are more enjoyable up to a point. 

I'll soon be able to answer my own question as I've decided to go for a pair of Momentum M400 MxV's.

@carlsbad2 Mono blocks also offer significantly more power if the stereo version of the amp shares the watts.  Love your system.  Hoping a "better" amp will move the needle.  I will report back.