Have you looked at Universal Devices isy994i? I am using it to control my whole home automation system, from lighting to temperature to irrigation to projector and screen, and yes, JRiver.
It's a very good and extensible system, and Universal Devices is a nicely responsive company.
I would *love* an integrated JRiver and isy994.
I might even take a stab at a JRiver plugin for the isy99r in the fall.