Interesting thread.
Sometime back I happened to try my old pair of SHL5 with a Parasound Halo Integrated and a newish Peachtree Audio nova300; both fine machines in their own rights. Even though less expensive, when SPL matched, I would say these solid states appeared to have given a tad more 'slam' (for lack of a better word) than my faithful McIntosh; or so I thought. However, when we swapped the SHL5 back to MA2275, interestingly, the comforting yet powerful and authoritative familiar sound returned; and I couldn't complain or bother to worry changing anything afterward.
McIntosh gets a lot of flak around, I should know! The idiosyncrasies of McIntosh aren't lost on me. American muscle, house sound, acquired taste.. the list continues. McIntosh is also known for rating their power rather conservatively. Added to this, tube watts are.. well, perceived different. But for what it's worth, my decade-old MA2275/SHL5 combo unironically still sounds sweet to my ears. Although, there is probably an unhealthy amount of intrigue around PrimaLuna’s DiaLogue Premium HP Integrated lately!
Recently I had the chance to listen to a pair of SHL5+ Anniversary Edition driven by a brand new Accuphase E-650. Now, one could argue that they aren't matched well with a price and/or power point of view. Regardless, this combination sounded beautiful to me. Just delightful. Not sure about the specifics of the rest of that particular setup, but being familiar with the Harbeth sound, including an appreciation for their Plus and Anniversary editions compared to mine, I would assume the major differentiator must have been the Class A beauty itself. The overall sound signature, if I dare say, was more in line with my own MA2275/SHL5 setup; perhaps with a better low-end definition. So that's that.
As with MA252, it certainly looks good on paper; could even be a match made in hybrid heaven. Only an in-house audition can help you really decide if they are a match for your fabulous speakers and the rest of your chain.