What is under Page's Marshall is a Rickenbacker Transonic cab with two high frequency horns; because of the angle of the shot there's the illusion that it's part of the PA. On Zeppelin's earliest US tours, they had a full backline of them, not because they were great amps(they we not)but because Page wrangled an endorsement deal so that the bands' UK gear would not have to be brought over(Page being tight with a shilling). The Ricky Trans amps were transistor, their answer to American Vox Super Beatle's with multiple channels and on-board FX, and just as shrill sounding. The cabinet design was trapezoidal, an 'inverse' to the Vox heads. One saving grace was that the cabs all featured Altec speakers with the white magnet cover. The speaker configurations were: one 15" and two 12", two 15"(probably what's over on Jones' side, but obscured), and two HF horns and a 15". Jones rig looks to be a 2000s head on two 200s cabs(to accomedate the width plus a 200s on top of the Ricky cab, and then a third 200s cab by itself. Obviously, with each subsequent tour(and they toured the US in '69/'70 multiple times)the increasing popularity of the band(and increasing money coming in)meant that they could afford to bring full Marshall stacks, as well as Jones' deal with Acoustic coming through, and they ditched the Ricky's. As far as their use of Sunn gear, probably in this situation, the equipment truck didn't get there in time for the show, and if it was indeed in Seattle, I'm sure there was plenty of Sunn amps available for rent, with Oregon being next door.