Do yourself a favor....Get the 2 barrell kit as well. You will use much less wood to heat your garage. A lot of your heat goes out the pipe on a single barrel. The second barrel is a heat exchange and really helps to utilize the heat. I have a 20' fan behind mine and am extremely happy with the whole set up. One thing to keep in mind though: The top barrel needs to have a removable lid (towards the back of stove). Makes bolting the 2 stoves together much easier.
I started out with a one barrel and upgraded.