I just used 2 smaller cans (I think 8 oz) of the same stuff from whole foods in a 6 gallon batch yesterday. It seemed like more than enough and gave the wort a very distinct orange color that I was very happy with. I suppose you could use more, but from what I've read it doesn't add much flavor, just color and some mouthfeel. The spices are what make this beer really distinct in the aroma department. I'm hoping the brown sugar contributes as well> I used 1lbs of brown sugar at the start of the boil.
The wort smelled amazing when it was done. I can't wait to try this one!