A few years ago I got the RAVEN LABS MDB-1, it is a 3 channel mixer/direct box. It works great for us who play both Chapman Stick and Bass. I can plug in it both sides of the Stick and a bass and mix their signals. The only downside is that it only has a mono output. But for small gigs it is a great tool, and it has a very clear direct sound.

Highly Recommended!!!

You lose the ability to use independent effects, but you gain the ability to provide a mono feed to a power amp and use a single, full range speaker cabinet (which is ideal for many reasons).

If the inputs handle line-level signals well, then you can expand to a fully independent rig via outboard preamps.

How about this one? http://www.sfxsound.co.uk/sp2/

Andy Salvanos used this on his latest CD and he told me it's a nice lower priced alternative to the Stepabout if you don't need too much EQ or the switchable routing. It'd be nice to keep in your case if you're traveling and playing thru a variety of amps which can be a crap shoot - especially w/a Stickup. It can be battery powered which is a big plus. It's simple but what it does - it appears to do quite well. I'm thinking about getting one.

Looks interesting, thanks!