With the Apple products you need a TV even though some control their dedicate macs through Iphone Ipod Touch every now and then you will have to login i.e. to load stuff into. For Apple TV which I have a TV is a must.
For the Sonos, I saw that once briefly in a restaurant. It does have digital out and there is a way to control volume on the BL5 without the BS9000 in place, I think you can connect an IR eye directly. I recall an article about that.
You will not be able though to run BS9000 and Sonos through the digital connection.
I considered a Sonus myself, however I feel this is one of these products where the look and feel is going to annoy me after half a year so I am waiting for Beomaster 5 / Beosound 5.
In the meantime I use my Apple TV which works very well. Its controlled through my BV8/Beo4 can't say that often enough.
JK
BS9000, BS2300, BC2, BL2500, BL3, Bl2, BS1, BV8, BC4, A8