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

Wow, beautiful system and house. What a wonderful place to enjoy music!

If you would like better performance I would look at upgrading your streamer and preamp. That is what looks to me to be constraints on your outstanding system. Look at the top of the line Aurrender to put your digital end in line with the rest of your system. For preamp I would look towards Audio Research or Conrad Johnson. 
 

A bit of a different point of view on @atmasphere ’s comment about price. Audio companies have different house sounds (“intentions”) and by moving up in cost of product the house sound is invariably improved. So, in this sense you get what you pay for. I have never heard a lower level component sound better than a higher level one. For instance moving from entry level Audio Research preamps to their flagship. However, you might prefer the house sound of, say Boulder better. So, if you don’t have a wide range of exposure you could consider a low level ARC preamp to be better sounding that a top tier Boulder. 
 

Alternatively. You could add a high end component to your lower tier system and it could sound bad because it just isn’t synergistic. But within sound categories you universally get better sound the more you spend. I’m sure there is a few exceptions or special circumstances, but in my fifty years I have not stumbled into any real concrete examples. 

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.

An Ad in the Link is from earlier in 2024, a very similar Spec' is on sale in the UK for £2K.

This Model Type and Spec' of Amp' will stand 'toe to toe' with Amp's up to 20 X this Value. I have been present and witnessed this this occur with the lowest and highest of the Neurochrome range. The lowest has stood 'toe to toe' with £8K Branded Valve Power Amp's.

There will be substantial funds reserved if the Neurochrome route to Power Amplification is adopted.

Such savings of funds do enable options to be considered to max out on the most desirable upstream supporting devices. Possibly even used sale item Speakers can be discovered, where careful selections are with the potential to create a ' Out the Ball Park' system for the price of Branded Off the Shelf Power Amplification.

If a device is bought from a Competent and Skilled Amp' Builder, there is nothing not to like about such a methodology to attaining a very impressive Power Amplification for a system.  

Those are good amps. Cost alone means nothing. You can always change if you don’t like the amps for whatever reason: to try newer technology or a different design, a different visual look/aesthetic, measured performance, or whatever you please. That’s totally up to you. I just would never ever make a change based on price alone.

Also always a good idea especially with big ticket items to either audition first or be sure to have a cost effective way out if things do not pan out as expected.

Mono blocks are only advantageous if you are switching to them from an amp that had high levels of crosstalk. A competently designed, high-power stereo amp can be just as good or superior.