The PAR is an DSP board with an IDE interface according to a magazine i just reread.
Then the bottleneck is the IDEinterface on the PARboard
What kind off image format does the PAR use and what filesystem???
If it´s propetary then you´re stuck.
Otherwise it could be possible to first connect the harddrive to an accelerated IDE interface like the PowerFlyer and render to that and the connect it to the PAR for playback but I´m not sure just guessing.