Went with the 525 quick-change kit from SC. Stock gearing. I do road and track riding, only one TD on the Pani for now but I don't see the need for different gearing. I'm not trying to win races anymore, just out there for fun at this point now...and get smoother on the new (to me) bike. Seeing that I bought the quick-change kit, I'll be more inclined to try different sized sprockets though so that option's still there.