PowerMax & PowerDrive
The Powermax series came out in January 1992, it was essentially a Concept One with onboard tools(and wimpy tool suction)
I had one of the maroon ones brand new, and absolutely hated it. It was clumsy, heavy, awkward, and ear-splittingly loud!
The PowerMax series initially used the steel agitator(in 2 and 4 brush variations) and then later had a plastique Elite style brush roller.
The Powerdrive series came out in 1994, and as mention was kinda what you'd expect to get if you crossed and Elite and a Concept One. The PD series used a variation on the Elite motor, and was considerably quieter that the Powermax before. I like the PD cleaners better, but the handle is too short, and they are kinda top heavy. A counter-weight spring for the handle(such as on the DAM) would have been nice.
New Powerdrives can still be found on ebay!
The PD series was replaced in 1998 by the Self Propelled Windtunnel.