I installed a 14 tooth front in place of the 15 and still have a lot of adjustment left on the stock chain. The pulls nicely up hills but will still cruise all day at 70 with quite a bit of speed left in reserve.
Wombat I have a 1550 pelican box on mine. They come in smaller sizes are pretty reasonably priced. They're also almost indestructible. I just drilled 4 holes in the bottom and bolted it to my rear rack using SS hardware and large SS fender washers top & bottom. You have to use a pad lock but for the money and beating they take it's a good option. You can kind of see what it looks like in the picture on page 3 of this post. I added 4 bungie buddies so I can strap stuff to the top.
As far as handgaurds I'm running the EMGO pro version.