I have not been able to get a good tone from the ubass straight into my walter woods (gasp!). The sound out of the instrument is naturally bow-bow and I want upright-like B'ohm-B'ohm. The highs have to be rolled back and the high mid (around 1k) has to be cut. The mid on the woods scoops out such a wide range that I lose punch and presence cutting it.
So my plan was to get a micro head (GK, Genz, Eden, etc.) and 2 identical small cabs (1-12, 2-10, 1-15, etc.) for smaller or bigger gigs. it was all thwarted when I was playing some GK rigs and stumbled on the MB115 combo. I could not duplicate that sound on any other GK configuration, not even big rigs or other combos. I was hung up on the low power (200 watts) and lack of extension cab option. I could not avoid the weight, tone, and price point of that amp. So I found a used one dirt cheap and got it.
I almost always have the VTBass inline for a second sound (pillowy bottom, smooth tube thumpy) it is on more often than not with any instrument, even with the upright it is a great alternate sound.
With the hollows there can be an impedance issue with some bass guitar oriented amps. Many newer ones are 1meg inputs and they work pretty well. But a piezo-specific preamp almost always balances the sound. It brings out the D and G strings, tames low end transients, and smooths out the highs and high mids. I like the Radial Pz-Pre and the L. R. Baggs Para-Acoustic. They both have the important piezo impedance buffers and tons of flexibility. Not hard to get a great tone even at the extremes.
I am lucky enough that the gig I sub on most with the hollow has a great house amp: An AI Clarus and Aguilar GS210. I only bring the VTBass pedal in.