Goodwin kit is one of the best. You could go to one tooth down on top, or one down on top one up on bottom. If you want lots of bottom end grunt do the second one.....but you better have a big track or some traction aid, espeically with Goodwins kit.
i know on my zr 800 i went from a 24 39 to a 25 38 (gearing for more speed) and did not lose a ounce of bottom end!! that thing had so much tourque on the bottom, it just made it faster on the top by a few!!!!