Can someone tell me how to use Logic Pro or Mainstage with Firebox? I'm using a Macbook Pro with my Presonus Firebox but not sure how to get this to my Mesa Boogie Roadking. I tried experimenting with a small Peavey practice amp, to prevent blowing my Mesa inputs. I've tried the the Line Output, but nothing. One of the sales reps at Apple told me he uses his Mainstage performing live.