Alternative to my P3ESR

@dekay makes a great point about adjusting crossover frequency and gain on your subs.  When I swap my Q7s in I have to adjust my subs accordingly.  I found that I needed to set the crossover much higher than I anticipated and am able to get them well integrated.

To pair well with a capable tube amp, you might want to consider the ATC SCM11 v2, which is known for its precision, imaging, and tight control. It can sound a bit analytical, but that character should complement a tube amplifier nicely to reveal micro-details and transient dynamics.

Have you considered that the amp might be the issue? The worst amp pairing I had with 2 different Harbeth models used KT 150’s.

What SS amps did you try?

Get a Schiit Loki EQ.

I have a setup similar to what you described, but am powering my P3ESR SEs with a Simaudio 600i.  I have a Power Sound Audio S1500 subwoofer (which is totally overkill) crossed over at about 80hz.  I don't feel like anything is missing throughout the frequency range. 

I recently had the P3ESRs in my main system (PS Audio M1200 amps / Herron Audio VTSP 360 preamp) and had some friends over.  They were amazed at what those little speakers could do in my large room.  So was I.  I had them about 8 feet from my listening position and augmented by 4 subs.  They of course run out of gas at higher volumes in that situation, but the imaging, soundstage, and tone were all incredible.

Alan Shaw says that they will run with just about any kind of amplification, but they like power and do well with solid state power.  I have the P3ESRs close to the wall with 4" thick absorption panels behind them.  I have gone through a lot of speakers, but the Harbeths while not perfect for my main system, are perfect for the small system in this room which is probably about 12' X 12'. 

I never say never, but I don't anticipate parting with them anytime soon.  I would try some better SS amps, experiment with crossover points on the sub, and try some room treatments before getting different speakers.