One new candidate is Ayre Acoustics's Series 8 line. The new VX-8 power amp just got a great review in Stereophile, although the corresponding preamp may not be a great fit.
However, the updated EX-8 2.0 integrated looks pretty close to a perfect match, at least on paper. The $8000 analog-only version (it'll sit behind an external DAC/streamer) weighs a mere 25 pounds, pumps out about 135wpc into 6ohms, has all the connectivity I need, including HT bypass & sub out) as well as unique features like the ability to disable individual outputs.
That last function is especially important because the Harbeths will also be used as the FL & FR speakers when playing multichannel content. That is, a multichannel source will be decoded by an existing A/V receiver that will forward the front-channel signals to the new amp. This means -- think about it -- when playing stereo content from a turntable, Tidal, or SACD, the new amp will drive the sub. The receiver wouldn't even be on. But when playing surround sources, the sub will have to receive a multichannel-mixed LFE signal from the receiver & the new amp should not be sending a second signal simultaneously to the sub. (I have a powered MartinLogan sub that can autoswitch between any of three line-level or amplified input signals, but should never receive two inputs at the same time.)
So from a functionality standpoint, the Ayre is the only option I've found that can do everything I need.
What I don't know -- and yeah, this is the same old problem -- is whether the EX-8 2.0 is a good fit with the Harbeths sonically. Stereophile's review of the original & 2.0 versions are pure raves -- praising even the built-in headphone amp, to my surprise -- but hey, so are half the reviews in the magazine.
So although I've made progress finding a credible candidate re: functionality, I'm still at Square One re: sonics.
Maybe I need to start another thread with a title that specifically asks about the Ayre/Harbeth combo. Unless any of the people here have tried that pairing themselves.