Pickup a TC Electronics Röttweiler distortion pedal yesterday, strictly for my bass amp. I did try it on my Peavey 6534+, but like every other distortion pedal I've tried it was complete overkill on the lead channel and I didn't like it as much as my lead channel sound when played through the clean channel. It might be good through the clean channel of the Peavey Classic 30 though.
Trying it on bass today I was able to get a much grarlier distortion out of my Peavey Mark VIII bass amp than I got with the distortion circuit of the MXR M-80. I turned the distortion circuit on the MXR off completely together with the 'color' switch and just used the EQ to boost the mids a bit. Very deep, growly distorted sound, no discernible bottom-end loss.
Also the SD Quarter Pound pickups and Hipshot brass high mass bridge seem to have fattened the sound up somewhat. Open strings sustain well, trailing off until inaudible around 40 seconds later. Given that's half a song in my current band that's no real use there, but I am looking to start up a much doomier sounding Amebix type band playing bass.

EDIT:
I watched this video before deciding to take a punt on it for $80 (as-new second-hand). The settings you see in my photo above give a more 'sensible' sound than on this video, however.
https://www.youtube.com/watch?v=fKuCql_5rmM