Following on from Saul's suggestion,
What about a pair of speakers built to match the main Soundbridge body. One would be active and the other passive.
These would click onto the roku chassis exactly the same way the end caps do at the moment so you just pull off the ends and hook these on instead.
The active one would sit on the same end that the power goes into the roku so you would plug the roku power supply into it instead, and then use a small link cable to then daisy chain onto the Roku itself. In the meantime, the output from the Roku obviously gets plugged into the active speaker with another pair of short link cables.
Finally, the cable run at the back is used to hide the wire (or you could build this link into the chassis anyway) that goes to the other speaker.
Now, granted the PSU that runs the roku might not be capable of powering much in the way of an amp, but it needn't be too big and it would mean I could by a 500 for my Kitchen
(I guess a bigger psu could come in the box with the new Active Speakers!)
PS - This is where I click submit and twig someone else has already suggested this - sorry!
PPS - If you go for this idea, I want some commission
(or other form of kickback!)