I agree with the previous poster. The pressure adjustment on the KPP doesn't really do much. That being said, I believe the pressure is less on the PX. It's just more comfortable on my head.
That's kinda a shame you're returning them because of the clamping pressure. Comparatively with the majority of on-ear cans out there, I'd say the PX 100-II is very much on the light side. Maybe it's just something that has gotten better over time? I don't really remember if there was more pressure in the beginning, but I definitely have many hours and trips on mine by this point.
px 100ii are now extinct and difficult to get-they are going for silly prices on e bay.
i saw a pair of KPP so i ordered them.
im very pleased with them and they have a very nice natural sound with a decent bass.
i play both through a first gen i pod shuffle which is fairly dark sounding.
px rules for comfort but both sound very good for the price