You are correct about the breakout cable. You can find that cable online at Markertek.com
I am currently using the Onyx 800r with my setup, much in the same way that you are intending to use it. However, I am using the XLR inputs. Either way, the converters on the 800r seem better than the 002's, and the preamps sound nicer as well.
Having a total of 16 inputs (8 from the 002, and 8 from the 800r) is also a plus, but keep in mind that if you decide to record at 96k, the 002 cannot receive more than 2 channels at a time from the 800r.
Hope this helps