Sorry this is late, I only just came across the post looking for something else.
Go to www.electrical.com
, visit the forums and send their tech Greg a message. He's building an Electrical Audio m&s decoder that should be publicly available in the not too distant future. You can buy early run models now, but there not cheap (about $1000 I think). If your after a hardware decoder I think you'd be hard pressed to find a better one these days without buying the Soundfield decoder which is closer to $3000!
Probably one of the sexyist looking things you could ever put in a rack.