I bought an RK aluminum sprocket/chain kit (-1/0). It seems to work well. Not too sure about the quality because I am new to bikes. One thing I noticed. My RPMs jumped up quite a bit, my gas goes down quicker, and my speedometer is 10-15mph off but I get some really quick acceleration; even at higher speeds.
Going down only 1 tooth in the front wont be that much of a difference. If you are only changing 1 sprocket make it the rear and go up like 5 teeth, or just do a 520 conversion and -1+2. Just got done doing that on my bike and wow what a difference. Make sure you get a speedohealer. Try Driven or Renthal If you cant find vortex.