Fender bassman 50
 

It's a good combo with a jazz bass to play medium gigs ?
Does it break up easily ?

Standard answer: it depends.
What cabs are you planning to run the amp through?

It's a small practice combo. How well it will perform for your situation is a question only you can answer.

Love the bassman tone. Always had trouble getting them loud enough for typical classic rock or "amped up blues" gigs.

Think high spl speakers without a ton of deep lows. JBL's, EV's and the like. From the Eminence line maybe a DeltaPro?

Gonna take lots of speakers no matter what to make them loud. More suitable for jazz, tame blues trio, small bars where you can't play loud, recording, etc.

Without more details, etc., I'm afraid the only answer is still "it depends". Real nice tone, IMO, if you can hear it.

Some BFM horn loaded stuff might be an answer. Those get louder with less power.

+1 on the BFM.

Make or have made 2 Jack 12's with the basic Beta 12A driver. Very efficient cabinet for a lower powered amp setup. Unfortunately I don't know from experience, I am setting this up as my 2014 project.

Sorry but I meant a bassman head running trough a fender cabinet..

If you do something like this, you should be golden

Rock!!!