Considering A SS amplifier

@neonknight , 
8 meters is a long run and might be the cause of your issues.
In your case, I would recommend some Audioquest speaker cables with DBS. Used Rocket 88, Rockefeller, or GO-4 isn't too expensive (relatively) and you might just score some on Hifi shark.
Is it possible to move your speakers closer? I have some cables I could lend you.
Bob

@neonknight
The only other consideration I got is speaker wire. Use Wireworld Eclipse Series 8. But need an 8 meter run so thats not a cheap test as I cannot find a run of that length on the used market.

8M is quite a run IF your PSA/BHK amp is already on the side of "soft" sounding. Rule of thumb to keep "speaker wires as short as possible" for home hi-fi, in general terms. Agree with gndrbob. Might be a culprit, or enough so to round things out a bit. A few questions.

1) I see those WW ES8s are OCC, "9AWG", are they standard or quad (bi-wire) speaker cables?

2) For a brief 1hr test, can you maybe move the speakers super close to the amp?

TEST:
Before you do, warm up amp, play a familiar track. Index volume at 10, 11 o’clock or whatever your normal listening level is. Make notes on what you hear with highs, mids, lows level of detail. Then power off, swap out speaker cables for super short runs.

Simple, cheap and crude test, won’t sound great, but this will confirm it quick. Go to Home Depot, get some wire to cut. Some use regular orange AC extension cords and cut them in half and strip.   Or locate the infamous 18/2 or 16/2 Brown Lamp cord (just for the test). Cut them at 4-6’ max length. Single or Dual-run cords if you can bi-wire. Move speakers close, 4-6’ from amp, 4ft better. Twist bare wire connect with no connectors if you have screw-in terminals with holes or wrap/pinch well - if doable.. Any difference, at all? Brighter, but grainy? Listen for louder volume output at same 10’oclock volume level, louder? Make notes, report back. Worth trying, cheap to do a quick test before buying other amps.

You say that the solid state amps you are considering are not available locally for a listen. If you have a local dealer, I suggest you audition a similarly powered amplifier(s) that he carries within your own system. This could give you the answers you are seeking. I suspect you are looking for a more articulate bottom end, maybe just a cooler listening room, or a maintenance-free component.

OK equipment rack is on the long wall, its a Salamander Geneva credenza, weighs about 130 pounds itself, and is needed to hold three turntables on top. Speakers are on the short wall, and they are JBL 4375, weigh about 190 pounds each. There is a fireplace between them, they are pulled out about 6 feet from the front wall. 

With the fireplace there its not possible to fit the amp between the speakers as its a stereo amp. Then that means a long run of interconnects, and even though I can do balanced it, I seem to recall that long speaker wire is more preferable than long interconnect runs. Now the AVM Essential are mono bock amps, so they could be located near speakers, but then you are talking an 8 meter run of interconnects. 

There is no way to move the component rack between speakers to shorten speaker wire runs. 

At one time I did use a Musical Fidelity NuVista M3 with these speakers, and they were quite lively on the top end. I was aiming for more refinement, but this is just too laid back. That was with the same cabling and speaker wire in place. MMM perhaps I did have the VH Audio interconnects in there, I might try blending some of those in on source components. 

I have experimented with the outdoor wire a long time back, I found it to be nasty sounding stuff. You would have to drag me back there to have to listen to it again. 

Oh and yes, the Eclipse 8 is a bi-wire arrangement. 

I am going to have to do some more listening with mixing in some VH Audio cabling. This would be a big move, and shouldn't be done as a knee jerk reaction.