I'm not sure how I didn't see this sooner, but Roland has just released a firmware update for the 7X7 expansion which now incorporates the amazing sounds of the TR-606 drum machine into the TR-8. At your fingertips, you now have the following classic beatboxes:
As to be expected, you can mix & match your sounds so that you can run with the kick from a 606, the snare from an 808, toms from the 727, and hats from the 909. For a drum machine nerd, such as myself, this is fucking fantastic!
Get all the info here!