I too think that "Never Ever" is based on "Amazing Grace".

In my experience the "how good does this keyboard play unmodified midi files" question almost always results in the answer "Roland". Their GM/GS soundset has always been very consistent in terms of the "feel" and volume levels of the voices.

Much as I love my PSR2k I always have to remap the midi file voices on any commercial or internet sourced midi files. The Auto Revoice option ought to help but I still find channel balance a big issue.