+1 for what you want in an amp. There are lighter-weight cabs out there, though, but these are good if you don't mind a little extra weight. And they go good with the amp. I'd get the 500, if it was me.
Then, there's the brand new Markbass Big Bang head (it has a headphone out). Looks good, but no reports yet. I'm running their Traveler 151P cab, and it sounds great. 44.75 lbs.
JimmyM, there are no reviews of the cab on MF. What do you say of it. And would you think I could use it with my LMIII and 151P cab? What would that be like, I wonder?