I am also considering this series.
An MB head and MB 4x10 cab.
Which gives me the option for a further MB 4x10 for extra "pose" and loudness.
Now that the initial reliability issues have been resolved, I have read that the only thing that is sub par on the MB series is that the onboard compressor, which is supposed to be a tad pants.
But nothing a pedal could not fix.
From what I have read, that the 4210 combo is very loud on its own.
All I need to do now is convince Mrs Dandelion that I deserve a new amp.