I think you know this area.
Since the devices do work under the shorter range and well, think about the designer's homes. I've been overseas and the homes are smaller, some are just one room so to start with 20 feet of coverage is not hard to imagine.
Dual channel is great and all but you are talking about mass production where they'll drop a headphone jack to make the numbers work.
I have a lot of tips over in the CNET Network forum if you want to try them.