Re: bass amp??? stupid question
I've run bass through plenty of Guitar heads (most notably old marshalls like the plexi and superlead)
will it damage the head? I highly doubt it unless the head was gonna break anyways. now, as far as speakers are concerned, Modern speakers can take quite a bit of abuse and still keep going (i'm not talking kicking them, i'm talking sound frequencies) however playing bass though them will wear them out faster. For older speakers you'll be pushing your luck if you play at volume levels much higher than moderate (of course, that may be "don't break the vintage stuff" paranoia, but i don't wanna find out) End result is playing at moderate to quiet volumes should be fine.
I played a old, hand wired 72 Marshall Superlead through some Mesa Boogie Deisel Bass 4x10s for quite some time, and it sounded great when i cranked it loud as hell. I never had any problems with it other than normal regular tube maintnance.
If you're after the type of sound of a bass through a guitar rig, you could get a cab loaded with 12in. Bass speakers and basically not have a care in the world (it would get you pretty close). Alternativly, you could try using Mesa Recto cabs (or some other cab designed for that modern high-gain drop tuned sound)... all the kids nowadays drop tune their instruments so far that they might as well play bass, and those cabs can take it just fine... that may be a bit of a coin flip though on blowing them/wearing them out fast at high volumes, but at moderate volumes, I wouldn't worry about it too much at all.