Well I think that kjones wasn't boosting any lows, there were plenty there with the accugroove already.
I don't know if he changed any tubes, but I highly doubt it.
I fiddled around with it for a short time, with my MTD, and then listened to his band play a song. I didn't stay very long, I had kids waiting at home heheh. Had to save my wife, you know

So, they were playing a sort of blues jam song, very jazzy to my ear. It was pretty long, with lots of parts, so I could really tell how he was fitting in their rehearsal mix.
Kjones has a great touch, his tone was everything I was expecting from that sadowsky. Very clear, with that p-bass roundness, some warmth, but basically what I would expect that bass to sound like.. just louder with crazy dynamics. He goes to do some solo runs and stuff, and just has to dig in a little to get that extra bit of articulation and snap. It was very cool. Nothing mushy, slow, saggy, boomy, or any of those other adjectives I see people describe tubes or the DB750.
To me this is surprising, as up until last week I played an EBS-HD350! You'd think I would HATE the DB750, as it theoretically couldn't be any more opposite from what I am used to. I should have my DB750 today, and I plan to use it at a gig tomorrow night. Though, it'll just be the direct out to our Bose PAS. (kind of off-topic heheh, sorry).