The reason I went for the Gustard was its class A and high voltage output so I did not have to add another box
Let me when you hear if you think I still need

I don’t doubt it’s capable for a moment, but it would be interesting to A-B a decent preamp in the system purely in terms of ultimate sound quality.

Hi Jules, a comment from my own experience.  I have two systems, one is an AV system first but I use it for music too.  I ran my Lindemann Source streamer/preamp (it has a "proper preamp") in my music system for well over a year.  I then bought the Gustard A22 for the AV system, I chose the A22 as it has the Gustard discrete class A preamp/line driver as well as the top end AKMs  I ran this for around a year in the AV system.  

I decided to stop being lazy and swapped the A22 into my main music system directly feeding the power amps and Lindemann moved to AV duties.  I prefer the A22 in the music system, this might be due to the DAC though the Lindemann DAC is also very good too - I prefer the Lindemann in the AV system, it suits the speakers better, arguably it has more "bite" which is better for AV. 

I don't feel I've lost anything by getting rid of a preamp from my music system, I may have gained.  You can argue that the A22 has a preamp inside it so what I've done is reduce box count rather than delete the preamp - except that I have no analogue input.  I could have used a preamp after A22, admittedly I've not tried this, I could do this with the Lindemann...maybe I should.   My main point is that nowadays a preamp is starting to look redundant in terms of box count but the DAC needs a decent output section to drive power amps well...in my view :-).  Even with my vinyl front-ends a fully analogue preamp is not required as my phono stage is digital (as you're aware). 

I would go further than that. In my experience they rob the music of subtle details. For me the way to musical satisfaction has been with the fewest amount of components in the signal chain that I can get away with. God knows how many resistors, capacitors, opamps the music has to go through in some preamps. I don't need the extra gain. Some say active preamps make the music sound more lively. In my case I don't need that extra life (whatever that means) and the trade off is just not worth it.

It does absolutely nothing for your signal to noise ratio. Why stick an extra gain stage in there when you have to attenuate it more with the volume control. Seems completely bonkers to me. I have even gone to the effort of thinking how to reduce the gain of my power amps to further improve my signal to noise ratio. 

Based on my personal experience, active preamps do have more life and dynamics than passives, which I have tried and which I would never go back to*.

Since I went digital and everything goes through my DAC, by far the best solution is to use the DAC's output stage to drive the power amp directly and implement the digital volume control. In modern DACs, this usually results in no loss of resolution down to very low volume levels. This is the best setup and beats using an active preamp afterwards. Why add another unnecessary stage provided the DAC has the output ability? You're just sacrificing resolution and noise.

*adding a buffer stage to a passive is fine and returns the life and dynamics to the sound.

I just tried egg sheets/trays to see if they helped in my room. If this worked, I was planning to get proper sound deflectors.
It does change the balance of my sound but not for the better I think this is down to the room
So I will not be getting any fancy diffusion boards as a backwards step

I've totally lost the plot.
What's a Vo?

Really glad it's working for you, John. Never thought I'd see you move away from open baffles but it sounds like the Evos are suiting you and the room very well.

Room treatment is very hit and miss and you can't change the fundamental nature of the room. For me, it works and I have it all set to make the room as dead as possible. I just landed on a double-garage as being the ideal dimensions. I guess you will have to experiment once the time comes to move.

Some people swear by the open baffle / panel bass, it is distinctively different from box bass. It's kind of lean and taut in comparison.
It can be fun for a while, but I do prefer box bass with its extra (added?) warmth and weight.

My recently departed Podium 0.5 panel loudspeakers were a fine example - I could admire the bass rather than love it.