Hello Vic,
Take a midi sequnce that you have created and try and find a store that has a good selection . You may have to visit a 2 stores.
Listen to how each keyboard plays a midi file.
I am pro Ketron/Solton keyboards . I have always thought that for sequence playback that Ketron is best .
Now inregards to editing midi files on the Solton keyboards, I have an X1 with a hard drive and vocal harmony kit . You have the ability to save sequeces directly on the hard drive . You can edit the sequence ( voice delete,voice changes,reverb settings,chorus settings ) while you are listening to the sequence . After renaming the sequence the changes are stored on the hard drive .
You also have the ability to copy that sequence into the internal sequencer if you like . You can alter or edit the sequence and copy it back to the hard drive .
It really comes down to sound quality. The Ketron keybords have always had the best midi file playback in my opinion .
Ketron X1HDV or the newer SD1 is my recommendation. You can email me direct oneils4@home.com , guitarcenterdno@hotmail.com or call me at Guitar Center in Towson Maryland 410 821 5200. Dan O