Once you get into doing LH bass with live drummers, your needs for a keyboard rig go up dramatically. Especially if you are trying to do LH bass AND keyboard patches, you are asking a LOT of any combo amp to do that and keep both ends of the spectrum nice and clean.

To be honest, most of the time I see people doing this on a full time basis, they use a separate small bass combo amp JUST for the bass (and stick it near the drummer, they like that!) and then a full range rig like you already have for the key sounds. Otherwise, the drummer has to deal with your keyboard sounds blasting him as much as the bass (and they DON'T like that!).

If your band already has good monitors, and sufficient monitor sends so the drummer gets a different mix from everyone else, you can skip this part... but split the bass off to a separate output if you can, no matter WHAT you use.