If you use chord inversions you can play most of the chords within 1 octave.
There is no reason to fix your split point even in a song, just store it in the preset(s) that you use for the song. (Split points can be put on any key and stored in the preset)
An arranger is designed to cover all types of music, including Piano and Organ.
Just because one person finds 61 notes sufficient, another person may not. (And vice versa)
Here are the ranges of instruments. http://www.4shared.com/file/61948604/2539e70a/Instrument_Range.html

Bill