Healy6er, my tube experience may be too ancient to help but here goes: I started out with Dynakits (PAS-2x and Stereo 70) late in the last millennium but the last speakers I drove with the Stereo 70 were either NHT Super Zeroes or the Cambridge Soundworks Ensembles. This was an unmodified ST70. I still have it; it needs some repair, but the idea of pushing it with the 990 (stereo, LF and RF outputs only) has occurred to me now & then. The problem, besides the work needed, is whether the ST70's 15-dbw power output would be enough for my 86-db sensitive Magneplanars, especially after the 20-dbw Adcom I'm now using. (Power output stated in watts is a deceptive concept, I'm not going to use it, and I wish Outlaw would have the guts to drop it and go to dbw: decibels above one watt.)
Most of what I've read about the listening benefits of tubes vs. SS has suggested that those benefits are mostly early in the amplification chain, which would imply a tube preamp driving a solid state power amp. But tube home theater stuff? Does it even exist?
One other thought: Musical Fidelity (look for them in Audio Advisor) used to sell a two-channel tube "buffer" unit that they said would bring the benefits of tube sound when mounted between preamps and power amps. Maybe someone else has had experience with it. I'm sure someone else can give Healy6er more useful information.
Re bass management, sorry but I haven't yet invested in a subwoofer. But I really, really like the 990's sound with the rest of my present equipment. Since none of it, except my AR turntable, is the same as I had with the Dyna preamp which I don't have any more, I can't answer any "compared with" questions.