UPDATE:
Why did Panasonic put model numbers out of order, in the case of the SL-MP## series? The SL-MP70 was a 2002 model, and the SL-MP80 was last year's model. But this year's model is called... the SL-MP75! (Target sells the SL-MP77, which is identical to the SL-MP75 with the addition of a wired remote control and the circuitry to operate the wired remote. The SL-MP75 lacks any remote-control capability at all whatsoever.) The price for either the SL-MP75 or the SL-MP77 is $59.99.
Just for testing and comparative listening purposes, I purchased an SL-MP77 yesterday afternoon. And I will compare it with the Sony D-NE300 (which seemed to have trouble driving the Sennheiser HD555 headphones).
One more noteworthy addition for Panasonic: Most North American Panasonic PCDPs made between 2001 and 2003 had compressed 40- to 48-second anti-skip circuitry which was permanently fixed at the highly-compressed 40- to 48-second setting, and could neither be set to a non-compressed/shorter-length setting nor turned off at all. This year, although I would have liked an "Off" setting for the anti-skip circuitry, Panasonic now offers a choice between 10-second non-compressed (oddly labeled POS 2) and 45-second compressed (POS 1) anti-skip modes for Redbook Audio CD playback, selectable either on the main unit or on the remote (depending on the model).