Post something on your website and include a note with every BHSE shipped out saying that the SAA cable voids the warranty. Should take care of any idiots actually buying it from those idiots.
The QNAP stuff is pretty nice but not exactly cheap and one thing to remember, rebuilding arrays on those things tend to be very slow. Don't be surprised if it takes a day or more.
This is extremely common with the 580/600s. You cam send them into Senn for repair or see if you can find someone to replace the contact. Another option is to just have someone hardwire the cable to the drivers.
Actually I think the Squeezebox is one of the better available transports, I don't think it'd be out of place in any system. If you believe stereophile's measurements it's jitter measurements are actually pretty low.
Routers are pretty simple to setup these days. I'd get something that supports N, even if you don't need that kinda speed the range improvements are worth it.