Blacky from Voivod gets his signature sound w/a Marshall 9001 guitar tube preamp into the input (yep, not the loop's return) of an ampeg or old acoustic bass amp. Sounds awesome.
My bassplayer uses a Peavey Rockmaster ---> input of an ampeg svt2 pro. Nut-shaking and crunchy.
For some reason, on bass amps, hooking the preamp right into the power section doesn't work that good. Sounds like blasphemy, but cascading both preamps works wonders.
For recording you'll also want to capture a clean DI for a neat and solid low end (low-passed)