One thing I haven't seen mentioned when buying a dulcimer, and it is important, is the length of the fretboard. I was lucky and bought a smaller dulcimer the first time around. My hands are small, and although I have a good reach because of my piano teacher, I longer fretboard on the dulcimer would be much harder for me to play, and there are already some chords that are really a stretch. If you can reach from fret #4 to fret #1 semi-easily you should be in good shape.

Chris