I have Wilson Sasha 2 speakers and also have had some issues with tube amps and bass control. I think that you received some great suggestions, including adding a subwoofer, using a loudness control, and trying a more powerful tube amplifier.
It probably is my bias (pun intended) and the type of music that I enjoy (violins, violas, and strings) but solid-state amplifiers are not a good solution for me. I recently tried a Luxman M900u ampilifier and a D'Agostino Momentum S250 amplifier, and although they were both great, I could not live without the mid-range timbre provided by a valve amplifier. I now use Audio Research 250SE monoblocks along with a Luxman CL1000 preamplifier (and an Esoteric X-01XD SACD player).
It probably is my bias (pun intended) and the type of music that I enjoy (violins, violas, and strings) but solid-state amplifiers are not a good solution for me. I recently tried a Luxman M900u ampilifier and a D'Agostino Momentum S250 amplifier, and although they were both great, I could not live without the mid-range timbre provided by a valve amplifier. I now use Audio Research 250SE monoblocks along with a Luxman CL1000 preamplifier (and an Esoteric X-01XD SACD player).