Pulse audio works well as previously mentioned. Can't say I've done what you're trying to do, but pulse is similar to ESD but newer and meant to be very network friendly. I use it both locally and to stream music to a laptop- it works great for this. I'd imagine you would point your audio out device to pulse which would be configured to connect to a pulse daemon that has the sound card / output you want to physically use. From what I recall about the initial setup is that I set up both client and server graphically with some of the pulse gui's for gnome and copied a special cookie file via ssh to the client.