How does that work? I'm assuming the receiver needs to connect to the network, the media center recognizes the receiver and from there I can apply zones to it and then control volume through JRemote?
Media Center does not control the receiver, it has its own internal volume control.
This means that all it can do is attenuate the signal.
So you would set your receiver to a fixed level, probably 0dB or the loudest signal you are comfortable feeding your speakers, and then use Media Center for all volume control.
Any device (or devices) configured as a zone will have their own independent volume level.
Media Center has Volume Protection and Startup Volume features which prevent playback from starting at high playback levels, and limits the rate at which you can increase the volume to prevent you accidentally going from 0% straight to 100% volume.
The only part I would caution you with here is that you want to be sure that nothing else in Windows can play audio to that sound device, or it might play at 100% volume. However that should not be an issue if you're just using the PC as a Media Center client.
What I do is configure Media Center to play to the HDMI sound device, while Windows' default sound device is set to the on-board Realtek audio (3.5mm speaker output) that isn't connected to anything. You could also set the default sound device to the JRiver WDM driver which is a virtual sound device that captures system audio and passes it through MC's audio engine. (meaning that the Volume Protection features are still in effect)