In my opinion combo isn't good solution for bongo. I don't know why but this is my conclusion. I curently play on 2x10 + head and B string sounds terrible. The problem is gone when I play 4x10
If You want recommendations write something more. Is this only to practice in home, how many speakers should it have 1, 2, 4?
Always a tough one... I used a MarkBass CMD102 - and it was ok. It handled the B but wasn't as deep as a wanted (don't get me wrong... it isn't terrible, just not what I was looking for). Added another 2x10 extension under it and presto - killer combo. My old SWR Silverado Special (2x12) actually was pretty good with a B string - but they are discontinued (you should be able to fine them easily on the used market)