Live or in the studio?
If it is studio (and a good one) then take a couple of options and let the engineer sort it all out. If it is live I would put the RE-20 on the Ampeg SVT and 8-10 and take the Radial DI. Run the DI clean to one channel and the miced SVT (maybe a little dirt) to another and worry about it (mix it down) in post production.
If you're gonna be stupid, you gotta be tough. - My Grandmother