Onkyo receivers are also controllable via RS232. I have both Denon and Onkyo and they are comparable.
I'm putting together my system at the moment, and I'm going Onkyo. Why? They're good audio quality for the money, have a range of good options throughout the range, and have well documented control codes. I need one from the TX-SR7xx range, as I need pre-outs for my seperate stereo (front left and right) amplifier. By buying the last model (while it is still available), I can get (a currently 706) for about 2/3 of the new model price.
I think this is a nice priced option. I'll let everyone know, in time, how I get on integrating it with linuxmce.