The Aphex 120A is bulletproof. I have three: L, R, and time code. The downside is that it is mains power only, but on the upside is that in addition to the 4 outputs it has a throughput. If it is wired into the cart and you don't need it for todays job it will still be throughputting to the Comtek even if it isn't powered up.
When I upgraded from a Cooper 106 to a Cooper 208 I removed the one I had rack-mounted on my cart because I now have enough outputs for most jobs. On a multi-camera (hardwired) job I typically place them at the DIT or Video Engineer's station and run cables to them. They can sometimes send sound to camera digitally through their fiber optic (if that works for you). The next task is confortably getting returns from the cameras.
http://www.aphex.com/120A.htm