Amp choice for Harbeth (SHL5)

I tried lots of amp/preamp and integrated with SHL5s. I listen almost entirely to classical music. I bought a Rogue RP1 tube preamp with a Channel Islands E-200S class D amp. The combination sounded better than many more expensive systems I tried, including all tube.

The best advice is to try some of the recommended amps to see which one will suit the SHL5s best in your system, to your ears. I can understand your remark of not wanting the SHL5s to sound any warmer as they do have a thick and warm sound. The SHL5s do sound a bit warm, thick and dull with most common solid-state amps but are capable of sounding lively and dynamic with few select amps. Some of the amps which are reported to bring the Harbeth to life are the Sonneteer Orton, Croft and LFD. I only have experience with the LFD. I now use higher-level Naim amplification with Chord cabling throughout (yes, the cabling also brought a relatively good improvement to the system).

In summary, what I think is if you can find the right amp for the SHL5s, the transformation can be an eye-opener. Music will just pour out from the speakers and sound very engaging, dynamic and full of life. (*a note is the source is also equally important)

I heard the Super HL5+ speakers in the Vinnie Rossi room at RMAF. They resembled my Quad ESLs, and I grasped where reviewer Paul Seydor was coming from when he wrote the same thing. From a 'stat lover, it is the highest praise possible. The setup included the giant-single-tube preamp module and the transformer volume control.

Different speakers, and out-of-budget amplification, but enthralling sound.

If you can find a dual-mode (ultralinear/triode), self-biasing PrimaLuna used within your budget, I daresay that one of the combinations of tubes/taps/modes should complement the Harbeths nicely, and should be fuss-free and reliable.

I have the SHL5+.  I initially had them set up with a Pass xa30.8.  It was wonderful.  I then (stupidly) tried a PrimaLuna Dialogue HP and it was awful.  I then tried a Bryston 4BSST2, it was good, but I longed for the Pass.  I now settled on a vintage Sony TA-N80ES.  I have it paried with a TA-E80ES pre and it really sounds great.  I won't be changing until something blows up.

Third for the Vinnie Rossie Lio.  Heard it on Harbeth 3 years in a row at AXPONA.  This year with the SHL5+.  
Tube linestage and capacitor store design isolates it from the AC grid.  Noise floor is unheard of and dynamics are incredible.  Stereophile class A.