For X10, you can use CM11A as an interface.
In what concerns the multi-room audio system, for any media director you have in LinuxMce, there is an embedded phone device, so you won't need anything else than a headset and a microphone attached to each MD, and you will be able to join all your MD's in a conference throughout your house. If you want, you can also define a VOIP account (there's a step in the setup wizard) or you can do that from the web admin (Wizard/Devices/Phone lines).
If you want to use a physical phone, those I know that work are: Cisco, Snom 200/320, BudgeTone
Hope this helps