i actually bought my diezel einstein head off our bassist =)
he was running his bass through a 16 i think band rack EQ into the diezel into a 8x10 ampeg cab, sounded killer
the EQ is a big thing in the signal chain, he's using a JCM2000 now , still sounds great albeit with a looser low end
have another friend who's using a jcm2000 into a 8x 10 and a marshall 50w jmp clone into a 4x10 , all for bass, sounds great, although he does have a distinct tuning playing style
i would also get a diff. cab if you're going to start doing that kind of thing often at higher volumes