Tube Amps With Good Bass Qualities

miostyn  I got lost with the subwoofer reference and tube amps.  The OP made no reference to that.  I've owned several subwoofers, mostly JL and of course all are solid state amplifier driven.  To your point of driving subs with tube amps you are correct.  But who does that?

The OP query references bass qualities of vacuum tube vs SS.  I own Sugden Class A solid state and Manley Mahi Mahi mono blocks.  The Sugden may have an edge with quickness, but the Manley mono blocks are musically more palpable and are not to be messed with.

To the OP, try the Mahi Mahi or the Snappers and be amazed.

From the perspective of someone who listens to a lot of electronica,  i have yet to hear a valve amp that can bring the fear factor in the sub bass. 
To my ears valves sound superior on acoustic bass instruments,  one tends to hear the leading edge with more definition, but the weight of the sustain doesn't match what a solid state leviathon can do. If you want your domestic system to do an impersonation of a superior stadium or club pa, ime you need solid state amps driving the subwoofers
Having said that, some of the most pumping reggae sound systems use(d) home made valve bass amps, and their bass was a force of naturr, redefining what bass meant, but undoubtedly those run primarily at higher frequencies than the sub bass in deep house, drum and bass etc

*nature

From the perspective of someone who listens to a lot of electronica, i have yet to hear a valve amp that can bring the fear factor in the sub bass.

I listen to a lot of electronia too. I started in 1972 when I heard Tangerine Dream on the local radio station! Since then ambient and electronia has always been an important part of my LP collection. Infinity Project put out an amazing LP called 'Mystical Experiences' that has some nice bass tracks, the second LP by Global Communication is great in that department and of course the usual suspects like Massive Attack, Future Sound of London, Forest Swords and so on- I'm always in search of the next best bass drop (but with some substance in the music, not just 'unce unce unce unce' for an entire record side...
My speakers go to 20 Hz no worries- and I've yet to hear a solid state amp that makes the bass as well. So much has to do with the amplifier/speaker interface though as I pointed out above. If you want a tube amp to play bass properly, then it should not be put at a disadvantage! A lot of people seem to want to make a tube amp fall flat on its face by subjecting it to a load for which it was never intended. This IMO is simply a waste of time and money- you want a tube amp to play bass then make sure you've done everything to allow it to do so and you will be rewarded.

 but the weight of the sustain doesn't match what a solid state leviathon can do.

This is so correct, all you have to do is play some sustained organ or similar to immediately hear the difference, and not just on subs, but on inefficient hard to drive floor standers too, and the winner is the one that tries to rearrange your innards.

Cheers George