Hi Ron, 
Yes, out of the box, the Ketron modules do playback midi files better than some others mentioned. I have tried this in the past and no matter how good the soundsource is, it will require considerable editing on the voices, effects, panning etc. for many of the midi files available on internet. So a sound module like SD-2 is a very good start + you will need some software to access the parameters of the SD-2 easily. I have heard some online demos of such softwares at    
Midi playback software   Give the demo a try and see if it suits you. I personally, haven`t tried these yet but the features do seem to indicate editing capabilities of the SD-2 voices and parameters.
Apart from a pure hardware sound source, if you are ok to compromise a little on the tonal quality, then online converters using sound fonts can give you a quick conversion =>   
Online midi to mp3  Some other premium software soundsources would be the   
EWQL Goliath  EWQL Goliath software
Good luck.