I have that exact setup, and I don't know exact THD or S/N numbers off the top of my head, but you won't notice any slight decrease in quality through the cable, that is if any decrease exists. One thing to note though: Eclipse is stupid, and unfortunately you cannot pause the changer like you can pause the CD playing in the HU itself (by pressing the "3" button).
It wouldn't be the exact same since the 3083 changer uses its own D/A converter as far as I could tell. You'd need to use a digital coax connection to utilize the CD7k's D/A but the CD7k doesn't have a digital input //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif