I've actually done a lot of experimentation with this. I even grabbed a JF SVP module specifically for bass. So far, I've found the best tones, using my RM100 (w/2x6L6's & 2xEL34's), into my Zinky 4x12:
Best warm clean and OD, is with my JF Vybe Deluxe. Gotta juice it with some OD, but the Vybe has massive low end and nice sweet highs.
Best crystal clear & clean, using a JF Twox on Bassman setting. Also juiced with an OD out front (tightens and brightens it up).
I've gotten the best results using a sansamp VT DI into the front of the RM100. I got decent results running the sansamp into the serial FX loop return. But, better to run it in front imo.
Also, I tried running my RM100 into a bass cabinet and it sounded like complete crap. So, don't even bother, lol.
Another note, if this is for recording, just use a good solid guitar cab, and run at low volumes, like 8 o'clock on the master. As long as you have decent mics and pre's, it'll sound best that way. If this is for live use, your gonna have to crank it and pray you don't kill your speakers, cuz it really isn't loud enough in a band setting... I don't recommend for live use.
Hope that helps!
Btw, I did not like the SVP module at all. Much prefer the Vybe or Twox. And, all of this is using my all stock American Special Jazz bass.
