Need advice from the gurus.

So, balanced connections but not a fully balanced circuit.  

That's ok.  Still worth getting hold of a pair of decent balanced cables and seeing how it sounds with using the Gato as a preamp with the monoblocks. 

Sounds like you know what you want you just aren’t hearing it in your system. I  would start with your speakers and then go from there.  One step and one piece of equipment at a time.  Have you heard a pair of speakers that you like?  Have you checked out local dealers and showrooms in your area?  I would find a pair that you like and try trading in the speakers you don’t want to help pay for the ones you like.  You’re on a musical journey as part of this hobby.  Take it slow.  Trust your ears.  Stay within your budget.  Make sure you can try anything you buy at home and can return for little or no fee if you don’t like the sound.  Most importantly, enjoy your music and your journey.  

jeffbij

... in a fully balanced system, the 2 channels are completely separated from the input through to the output ...

I'm not sure what you mean by 'two channels" and the term "fully balanced" is rather ambiguous.

In a balanced circuit, you'll have a separate positive, negative, and ground for each channel.

... while something that just converts single ended signal (in and out) through an op-amp to XLR connections is different.

Use of operational amplifiers (such as differential amplifiers) are common in balanced circuit designs.

@cleeds 

I'm not sure what you mean by 'two channels" and the term "fully balanced" is rather ambiguous.

(Just to stress, I am not an expert.  This is just what my understanding is, which maybe wrong.  So I welcome better clarification and a chance to learn.)

The two channels are the left and right channel.  And what I'm referring to, and on a very basic level, with "fully balanced" being when the circuit maintains the separation of the positive, negative, and ground (i.e. 'balanced') throughout ALL 3 sections of each channel, the input, amplification, and output.  This also requires that the left and right channels can not have a shared or common ground anywhere in the 3 sections.  

That said, what a lot of preamps, amps, etc. will do is have a balanced input connection, to an op-amp which converts the signal to a single ended (i.e. common ground) amplification section, then back through an op-amp to a balanced output connection.  (again, my simplistic understanding). Thus, while the signal is balanced in and balanced out, it is not "fully balanced" thoughout the circuit.

Which leads to the OP quote from 6moons about the Gato:

This is per 6moons regarding the AMP-150, I assume the "AE" version is identical.

"The input PCB sits near the back plate and sports NEC relays and an analog BB PGA2320 resistor-ladder IC. As a single-ended circuit, the XLR i/o ports are convenience items de/symmetrized by a TL07a chip."

- Jeff

jeffbij

... "fully balanced" being when the circuit maintains the separation of the positive, negative, and ground (i.e. ’balanced’) throughout ALL 3 sections of each channel, the input, amplification, and output ...

By your definition, an amplifier using a differentially balanced circuit isn’t "truly balanced."