You could cut the original 600 cord down to size as you suggested. Then, you could buy the 650 cable as a backup or replacement. It's a better cord anyway--in thickness and ruggedness--not sound.
Anyone know of an INEXPENSIVE 4 ft (or so) cable for these? The 10 foot is a bit long. Not looking for fancy-schmancy magic cable "properties", just shorter length. I tried a search but couldn't find anything.
Edit: I may just buy a cheap replacement and cut the cord to desired length and re-solder the plug on.