I typically play through an Ampeg SVT, V4b, or a non master fender bassman 100 so I know what you mean. I haven't needed much elseI thought you were kidding, there's a certain swell, bloom, linear OD, whatever you want to call it from tubes, that I can't get from solid state, the response seems so much more natural and attached to the bass in my opinion. A lot of times, because of how the maker worked it up, they get a bad rap for being saggy, lazy and not responsive to the dynamics from the bass, but when it reacts correctly it can be amazing, and give that 3D warm feeling people refer to. Honestly the best circuits I've played incorporated both tubes and mosfet, I have a totally tube driven head and its nice and tubey, but that's when the lazy, squishy feeling comes into play, Ashdown Power stage helps, but in my experience unless you're cranking the power tubes you're not going to get that part of the equation, but you are right there, preamp/power amp together is really magical, ie SVT/400+/V6/AD200B
I like some of the solid state offerings available today, like bergs and quilters. I just don't see a "tube tone" being had without a full tube amp. The best thing about all this though is the subjectivity of sound. I love hearing other people's opinions of their favorite tones, all the t00b discussion as of late has been entertaining. The sunray - > archetype rack clips from the other day were nice but just not my idea of thrilling tube distortion