do you plan on running both into the front "special sauce" input? If so, then you'll want to pay attention to the Global settings for input level (for the analog-to-digital conversion). Bass tends to have a lot more energy due to transient peaks compared to guitar, unless you are playing in a very "measured" manner, purposely playing bass so as to minimize those dynamic transient differences.
Otherwise, have at it. Start with any of the 5 bass amp models, or either of the Bassman models, and audition the tones through a variety of cab block IRs. Personally, I prefer the cab pack 11 Ampeg 4x10 collection, and the recent Ownhammer Ampeg IR pack.
If you're looking for something more modern metal with a drop tuned bass, then things get a little trickier: parallel signal paths with hi-pass+dirt on one path, clean fundamental tone on the other. Lots of ways to muck around and get lost doing this kind of thing...personally, I like getting most of my tone from a simple core amp/cab block, and then add parallel mixed ear candy to that primary tone.
cheers!