Just know that the piezos do not output to a 13 pin connector to be used with MIDI devices. The piezos go through a potentiometer to blend the sound into the main line coming from the magnetic pickups.
I had a 6ii and sold it, and I miss that bass a lot. Being 19mm string spacing and 35" it was a big beast, but the sound spectrum was quite amazing, really could go from a high treble/bass sound to a mids-trombone sound and cut through whatever
Any of these basses, MIJ, the older the better, highly recommended