I hope you don't mind me asking an obvious question, but have you actually tried the DPX1 with a PAL progressive scan player.
Just because Yamaha literature doesn't state that it accepts PAL
PS, it doesn't necessary mean it won't accept it.
Take the Panasonic AE100 for instance, the handbook and Panasonic tech helpdesk all state it does not, when in reality it does.
Because there were/are legal implications regarding PAL PS apparently, manufacturers may be a bit coy about giving the full picture (no pun intended).
Robocop