Keep a 15t front, go bigger on rear.
SuperSprox Stealth is about the best option.
+1.
I switched to a 14t in front and it accelerated the wear on my chain - I think it has to do with the increased angle as it wrapped around the sprocket. I used to get 20K miles on my big Kawasakis, won't get more than 12K on the Monster.
SuperSprox is also a pretty good recommendation.