I own a PB 800 and 1 CAB 67 rated at 8ohms. at 8ohms the head is producing 400W rather than 800W at 4ohms. My guess is that Phil Jones designed the amp to play through 2 CAB 67’s which would give you 12 7 inch drivers in parallel to produce 800W at 4ohms that would be massive. 6 7inch speakers move roughly the same amount of air as 2 12s or 4 10s +/- but with less mass per speaker cone resulting in quicker transient time which equals more articulation. Also his design places the resonance point of the speaker at around 34hz which is a little below B 0 at about 31hz and D 1 which is drop D which is around 37hz. All that nonsense aside, I play a fender fretless precision bass and I can say for sure that i’ve played through many amps, GK, Mark bass, Aguilar, I also have a pristine 73 Ampeg V-4B tube that I have played through the Cab 67 and almost every time asking around and every time talking with other players they choose the 800 head with the 67. As bass player I learned a long time ago that nobody listens to bass players other than other bass players. So if you’re chasing your sound PJ is well worth looking into, but like all things, it’s not for everyone.