OK. That is sort of what I thought you were getting at.
You could do this, but the CasaTunes interface would only control the XLe. We only control one controller, which is determined in CasaTunes Setup. So, if you purchase the XLe, it would be the controller you would pick in Setup (actually, this is done automatically in the case of the XLi and XLe). Then you cannot control the Russound with CasaTunes.
If you do this, there are a couple of things you should remember:
1. Set all the outputs to always be at sound output level of 70, with flat frequency response. This gives you a nice strong, clean, signal to the Russound inputs and then you would use the Russound controls to control the room volumes, treble, bass, etc.
2. To get 9 sources, you would need the XLe and have it running on Vista or 7. You can get a total of 9 “internal sources” by plugging motherboard audio into the XLe’s “external inputs.
3. You will not be able to control the Russound using CasaTunes, even for the ports that are set up like your existing system (2-6).
4. Rooms listening to Port 1 will all have to listen to the same CasaTunes source. In other words, if you chose to listen to source 8 using port 1 in one room, any other rooms that are listening to port 1 will have to listen to source 8. So, you can still only listen to a maximum of 6 ports throughout the house.
I think the best bet is to replace the Russound with the XLe. You could use the Russound as an amplifier for the first 6 rooms by having port 1 go to room 1, port 2 to room2, etc, for the first 6 rooms and you would need an additional amplifier for rooms beyond 6 rooms (hope I am making sense). Even this is not perfect, since you could have volume control issues and power on/off issues trying to use the Russound as an amplifier.