The board only has 6 available PWM outputs and those are being used for the left and right ramps. If you were willing to share colors between the ramps or between one ramp and the topper you could split the signal.
Alternately there are four open and usable digital pins. That's how I was doing the synchronized under cabinet light demo. That was driven by a board that uses a simple serial protocol (the shiftbar from www.macetech.com) so it could set the left and right strips to match the colors of the ramps.
I have no idea what is in those little self contained remote controlled RGB lights like the pinballtoppers.com speakers use. It might be trivial to connect to them, but it's more likely to be a single unmarked chip covered with epoxy.