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

I think you might see a bigger improvement by changing your preamp. You have good amps.

t 

only if the upgrade exceeds 57K

 I've been considering upgrading these amps to the next price/quality level.  My biggest concern is whether I'll get the level of improvement in SQ that will move the needle.

@skinzy 'The next level' has little to do with price just so you know. High end audio isn't driven by price (although many think it is), its driven by intention.

On top of that there's something called the 'Veblen Effect' which causes people to think that if they spend more money they will get more value. Sometimes that's true and sometimes it isn't!

Put another way it sounds like what you really want is something that sounds better. That may or may not be the amps. FWIW, sound quality always starts with the source- get that wrong and nothing you do downstream will sort things out. If the source is right, the preamp is the next step.

Since you are running a balanced power amp, consider this: there is a standard for balanced lines which I've found many high end audio manufacturers seem to ignore. If the standard (AES48) is supported, then you'll find the interconnect cables to not contribute to the sound of the system- they will be far more neutral (which is part of the goal of using balanced lines, other than elimination of ground loops).

A post made in previous threads follows:

"  

I feel like I have left out a recommendation of a Low Powered SS Power Amp' that has thoroughly impressed me during demo's in a variety of Build Models, which I made known recollection of experiences had on this forum.

 The Neurochrome Modul 65 has been in use in my Local HiFi Club as a SS Amp' demonstrator for quite a few years. This Amp' had been used in comparisons to both Valve Power Amp's - Valve Integrated Amp's and the same in SS.

It has been used driving Quad ESL's both Vintage and Modern, as well as much kinder loads for a Speaker.

Where it really showed it strengths, was at a time when it proved quite difficult to separate its presentation qualities during a comparison to a EAR 899 Power Amp.

With the resident 899 in the system used, the system Value is close to £50K

With the Modul 65, the system Value is closer to £40K

Neurochrome Amp's are today my top of the list consideration for Amp's when I retire from using my system that is totally Valve Orientated. 

FYI, In a £200K System with a Soulution Power Amplification and a value of approx' £150ish K with the Neurochrome Modul 686 as the comparison Power Amp', the system was just as impressive with the 686 included. some from the short term demo' received made their preference for the 686 known. The system owner was usually an outspoken individual, which following the demo' was not too outspoken, "

In your system I’d first look at a better streamer from Innuos, Aurender, Grimm, etc.  The Zenith is really good, but I think there’s a good bit more to potentially be had there.  Just my $0.02 FWIW.