Interesting.....I may go with the 600 then. Oddly enough Im not really sure why my bike has super custom cranks ( I think my parents may have upgraded it years ago before I inherited it) as I have the original manual for the bicycle and it says it comes with the 600 cranks......

Are the 600EX cranks very heavy? Would I be better off to go with something else that is vintage yet a bit newer / lighter?