um. I'm able to send the same stream to all of the squeezeboxes and media directors in my house, simply by selecting them on the floorplan. It's not lock step perfect in sync, but it does work.
As for multi-zone amplifiers, the setup of such equipment is insanely complex... on top of which, we need users to build templates for multi-zone amplifiers..
honestly? just use a squeezebox.
-Thom