What solid state power amp are you using with your Harbeth Super HL5+ speakers?

I'm using a 60W Hegel H90 with my HL5+. The pairing produces holographic imaging, a deep black background, detailed midrange and well controlled bass that is deep and powerful when it needs to be. It sounds clean.

While it can facilitate some magical moments (the singer and band is in the room, etc), I find that it rolls off a bit of the high treble, hence the black background. This is apparent once I switch to another amp that is slightly  more organic but a bit more vague in soundstage (an Audio-gd Precision 1 amp).

Despite that, ambience and reverb are still very much present and immersive with the kinds of tracks that emphasize them.

They are also in a small room, 10' x 12'.

I have the Harbeth Super HL 5+ 40th Anniversary speakers and I'm running them through a Pass Labs int 250. Absolutely love the combination. Sounds superb.

Using a Parasound a21+ driven by a Rogue Audio tube preamp.
Sound is as good as I could ask for.  Super smooth and refined.  

Using the SST Son of Ampzilla II with mine - 220W. LTA Microzotl MZ2 tube preamp. Tried the Benchmark ABH2 as well, didn't think it was underpowered at all at 100W (and I have a big room), but didn't like the sound as much. 

@routeman21 
Looks like I missed something important in your initial post:

Your impressions. I’ve been using a Conrad Johnson CA-150 (SS) integrated with my Harbeth SL5+ and the sound is nice but is underpowered at 135W@8ohms. Also, I would like a little more refinement with the amp.

My impressions of the following (from my previous response):

I have driven my SHL5+ 40ths with:

• Bryston BP26 pre > Forte1A (class A 50 wpc)

           - 3rd place in refinement.  
           - First in musicality (non clinical?)  
           - Not as open sounding at higher volumes driving my B&W                   801 Matrix S2s or Maggies.

• Bryston BP26 pre > Michael Yee Audio PA-1 (class A/B dual mono 100 wpc)

         - Still kind of new to this one (less than a month of recent time               with it since the move.)
         - Sounds a bit clearer than the Forte1A.

• Bryston BP26 pre > Ampzilla 2000 2nd Edition (class A/B 300 wpc monoblocks)

           - Close but clear 1st place in refinement but better than the                    rest all around.  Especially at very low and moderately high                volumes.             

• Hegel H190

           - 2nd place. Very close to the Ampzillas in refinement.
           - Possibly best match for the SHL5+40s up to just over                         moderate levels where the Ampzillas can just keep opening               up to higher levels

These impressions are based on 5 months in the new listening space (14 x 17x 9 wall to wall carpet, bass traps in the upper corners and some other minor treatments).
I work from home in my listening room so average over 5 hours a day listening.
I am also still a bit new to this hobby but have been a classical piano student throughout my life.
I listen to jazz, some rock and mostly classical piano.

Flipping the direction here, the Harbeths sounded better with these different amps overall than several other speakers of different types I keep in rotation.

Hope this helps!