Last night I hooked up the Pioneer CD changer into the C-9 input and then C-9 output to the 990 aux in. The C-9 can be set to bypass or engage the processor. WOW!!! the imaging and wider soundstage is AMAZING. Using only the front and left channels, I can hear the sound enveloping around the back as if my surround channels are active.
One thing I noticed though is that I seem to get much volume in output when engaged than bypass mode. I haven't noticed any distortion at all at -10 volume setting... and that is pretty loud.
Now, I wish I can have this in the loop for all the analog sources I have connected to the 990.