M30.1 is my least favorite speaker with the Harbeth line (M30 is worst with rolled off treble and a warm and dark sound). As others have mentioned, the P3ESR is worth considering. Another option if you want to get out of Harbeth is Marten, either Oscar Duo or Duke 2. Be prepared to upgrade the rest of the components to get the best out of the Marten as it is a very revealing speaker which will reveal any shortcomings with partnering equipment and cables.
Back to trying to upgrade Harbeth 30.1s
I'm hoping someone has done some of the work for me. I've upgraded everything else and now I'm back trying to improve on my Harbeth 30.1s. The issue is space. I need either another stand mount or a small floor stander with a similar footprint because of my listening space. I'm 8 feet from the speakers, so it's near field listening. I'm generally happy with the Harbeths but I'm hoping to squeeze out some extra dynamics and bass without sacrificing tonality. Especially interested in anyone that has done listening tests with the 30.1 vs other speakers.