I have 30.2's and drive it with a Luxman 590AXII that has a bi-passable loudness control. They sound wonderful at low volumes. Yes, I know, tone controls are looked down upon. However, as Ccakyol stated and mwinkc chimed in, a loudness control is what is needed at low volumes. It's one reason I went with the Luxman, aside from the Class A power, as I wanted something close to tubes without the heat and tube issues. I don't think changing speakers is the answer. I am sure you'd hate to part with the Line Magnetics, but I'd say it's not a good match for Harbeth speakers. I am lucky enough to have a Stereo store close by with both the Harbeth and Line, and I did not like the combo. YMMV.
Recommendations for speakers that sound great at lower volume levels.
I have a pair of Harbeth SHL5 Plus and they sound wonderful when I crank them up. But at moderate to low volume levels they sound disappointingly flat and unengaging - instruments are less palpable, bass has less bloom, and soundstage has less air and dimensionality. I drive my speakers with a tube integrated - a Line Magnetic 845 rated at 26 watts of power. My Harbeths are rated at 86db. Would a higher sensitivity speaker be helpful? Or how about a good quality small shoebox sized pair of speakers coupled with a subwoofer? Or not. What speakers are going to deliver music you can feel at low volume levels? What say all you wisened audiophiles?