If all you're wanting is a relatively small change, then I would try to do it with tire size. Go to tirerack.com and find the tire size you're running now. Then find the column on the specs page that lists diameter & how many revolution per mile. To effectively lower the gearing you need to decrease the diameter/increase the revolutions per mile. A calculator can help you figure out the difference by taking the known values in current tires and figuring what the new ones will do.