Looks like if you go in for it now, you get that box for free. My big couple of questions about it have to do with genre->album->artist browsing and whether it will support multiple tag values. IMHO not being able to browse by genre (as in subsonic) is so crippling as to make a music server suboptimal enough for me that I would never pay for it.
The multiple tags thing sounds funny, but I use it for things like making a track "Baroque:Viola da Gamba:Chamber Music" and being able to find it from any of those. I know the tag spec doesn't support it, but I don't really care: making each tag unique like that is IMHO a severe malfeature. Sonos just chooses the first tag value it sees. I got a sonos play for my bedroom, made a copy of my music with one genre per track, and find it really crappy to browse.
Sent them an email, it will be interesting to see what they say. If these things are done, could be a pretty cool thing for me.