Harbeth 30.1 or 40.1

@gte357s   Yes, I agree it's tremendously confusing.

There have been reports of really excellent performance with Vinnie Rossi products, that aren't that powerful and have a tube front end.

Likewise, many swear by the combination of the LFD NCSE which is only 70W in its most powerful incarnation.

big_greg just posted above, and I also know of someone very happily driving them with a Linear Tube Audio LTA Z40 integrated, which is under 50W.

So there's a real diversity of opinion; I can't think of an example where there's more diversity, actually.

If you like the sound you're getting, perhaps there's no need to change.

My suggestion was to perhaps try to borrow a powerful SS amp just to see what difference it made (particular in the bass region).  On the other hand, tube watts do tend to be more powerful than ss watts, so perhaps try and borrow a 75W push-pull or ultralinear tube amp.

If you go on the Harbeth User Group website, you'll find a thread with owners posting lists of amps they've used.  Shaw has some pretty extreme views on amps, but it's very enlightening to see the range of models people are listing.

The 40.2's at Deja Vu were, for me, the best audition--the best-sounding speakers--I've ever had in an audio store.  After just a few seconds of a Beethoven piano concerto I let out a "wow".  If I could have 75% of that at home I'd be a happy camper.

I'm less sure about the 40.1 but there isn't an absolute need to drive the 40.2 with more than 60 or 70 quality watts.  Yes, perhaps more is better, but quality is also better or quantity.

You'll need to add sub(s) to the 30.1 to get the bass quality of the 40's, so something to consider when considering financial outlay.  I agree, though, that you can only ultimately tell at home with an audition there.

Vu of Deja Vu, who's a major Harbeth dealer, stated to me that the 40.2's needed 2' of clearance from side walls and 3' of clearance from front wall (behind them), all measured from the relevant edge of the cabinet.  The experience of the gentlemen in the link I posted earlier suggests that you can get away with less and still get very satisfying sound.

While I've only heard the SHL5+ in stores (e.g. in Seattle), it always struck me as cut from another cloth, and aiming to do something rather different.  Just look at the drivers that it uses.  I heard the 30.1's at CAF and thought them excellent when driven with a high-powered tube amp.  It was the 40.2 iteration that sought to deal with the bass issues, over the 40.1, and are indeed much more domestic-friendly.  I don't understand the comment about 40's being too loud--there is a volume control, after all.  The 40's are large, awkward-shaped, and heavy, but that's what you pay not only to get the bass extension but also the wave-launch from the wider baffle that provides a more realistic impression of real instruments in real space.

@arturgorniak is the extreme case of someone who believes 40 series Harbeths need serious power.
https://forum.audiogon.com/discussions/harbeth-40-2-40th-anniversary-with-simaudio-mono-blocks
At the other extreme, I've read posts from people driving them with tube amps well under 50 W.
But I think you are reporting the lowest.
For a real comparison/contrast, I think you need to aim for 100 or 150W SS.