A Yamaha PSR-S900 or a Roland E-50 would both be good choices.

There's also the Yamaha PSR-S700.

If the folders on a USB device, or a Media Card were made smaller, then any of instruments would have no trouble reading MIDI files.

Ian
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Yamaha Tyros4, Yamaha MS-60S Powered Monitors(2), Yamaha CS-01, Yamaha TQ-5, Yamaha PSR-S775.