I too am interested in bass synth sounds. I have a Roland V-Bass pedal with the GK 3B pickup on my Yamaha 5 string.
I can't fault the tracking. Biggest problems are, a, the physical size of the pedal board and b, the limited sounds available. I have been looking at the Roland GR series to use the GK 3B pickup with but only the (hideously expensive, for what I want it for) GR55 accepts the GK 3B pickup. (I could be wrong here...)
Any one know of a compact pedal that will accept the GK 3B signal? I don't need all the bells and whistles, just useable sounds I can mix with the bass signal.