I've owned the M30s and now the P3. The Purist Poseidon speaker cables made a dramatic change in the P3s, making them sound much bigger and with deeper, better bass. I never tried them with the M30s, but I think it's worth looking into. Sounds like they might give you exactly what you want.
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.