I've tested the pedal. But please bear in mind that I'm not a distorted bass fans (I bought the pedal for my guitars), so I don't know exactly what is good or bad bass distortion sound.
Onto MIA Crunch Box. It sounds huge but I cannot keep the lows without being muddy or lost of definitions.
Then I plug in another MIA pedal :
This one sounds better IMHO than the CB as it has 3 band tone control (I think it's active) so it is more flexible. It also has a "symmetry" control so I can go from mild overdrive (sym knob max position) with the note definitions intact to all out distortion (sym knob min position) and the variation of them in between. I can even get Ampeg like grit with it (imagine Geddy's solo on Vital Sign). I think this one is more suitable for bass than CB. The only problem is: the pedal is very limited, mine is part of 92 units built by MIA's for Australian Red Cross charity.