I was considering the LB550 but realised it makes no sense:
My RM800 does small, light and loud and the drive circuit does a very good valve-esque bloom
My LB30 and CTM100 do valves, neither are particularly cumbersome.
My ABM has a valve drive circuit in the preamp which sounds pretty good too.
I have no gigs even without lockdown.
Don't therefore need a small light loud valve-preamped head.
Can't believe I'm being sensible.
Oh well, off to look at some bass guitars instead. Sanberg Lionel, ACG, Marooooschick etc here I come.