I play a 1980 4001. In '06 i put brand new 4003 pickups in it when the original neck pickup died. I used to own a couple of 70's Fender Bassmans, used tons of provided backlines with various unmemorable 8x10 rigs. And who knows what else. Most times the performance was so much more important than the brand names of the gear that we often times didn't notice what kind of amps we were using. I usually disliked the new rigs, tone-wise, and almost always liked the old ones, especially ones with tubes.
I've found that I like the vintage Acoustic Control Corp amps by far the best with my bass, especially the 320 since you can use both channels and go Rick-O-Sound into it. The 150 series isn't quite as great, but still sounds good, can be found for super cheap, and can keep up with 2 Marshall half stacks while running at 4 Ohms, if necessary. I probably shouldn't post this, but most people seem to have no idea how loud and good-sounding these amps are, so you can get them super cheap, considering what they are capable of.
Next best sounding, yet powerful-enough-for-gigging amps, in my humble experience, would be the Ampeg V4-B, followed by the SVT. I've never owned either of these, but have loved every single different version of each that I've ever used with my Rick. These amps are fantastic. They are classics for a reason, but everyone already knows this, so they tend to be very expensive.
Next would be old Fender Bassmans - again, tubes, plus 2 channels that can be used simultaneously which is always nice with a Rickenbacker.
After that, this is where different amps I've used become indistinguishable to me. I'm sure that there are tons of great ones, but I was just too ignorant to be able to figure out how to make them sound special and interesting.
I am no expert. I haven't used everything out there. I just love music and these are the amps that stand out and make my Rick sound like the music I like to listen to.