Likely gonna buy one of these babies tomorrow!! But: why does the one in the store have a (U) after the model nos, as opposed to the more usual (S)? is this model switchable between 50/100Hz? I've already been through 2 PK25s and 1 PK3 from the store and I guess they're growing a mite impatient with my fussiness and the Pannies were terrible for 100Hz artefacting on the footie - to say nothing of the bent verticals, moiring and dark margins!!!!