Ha, that's exactly what I found with my MJ4...sounded kinda meh with the stock strings which, IICR, were D'addario nickels. Which is odd because those are my default rounds for all my basses, and I normally like how they sound. Installed an old set of
TI Jazz Rounds on the MJ...voila...the bass came alive.
I may be mistaken but I think the M-2000 and the MJ share the same mil spec preamp, which might explain why two basses with very different pickups are both very picky about strings. That's pretty much the opposite of my experience with typical MFD pickups (with or without a pre), which seem to sound great with every string type I've ever thrown at them.