928S - I have the FE2 with 18" wheels.
Since the road noise factor has been brought up, I'm more aware than ever with regard to keeping a sharp ear when I'm driving at higher speeds. I still stand behind my claim that this is one very quiet car. I compare it about equal with my brother-in-law's 535xi, which I've driven a couple of times.
I know that MoFex and 928S are auto enthusiasts like myself, and I'm sure they know what they're talking about. This makes me believe that there was some type of omission of sound deadening material on certain cars.
Excessive road noise is also something auto writers will complain about fairly often when reviewing cars, and I haven't read any review that has criticized the CTS for this. If anything, the reviews have on occasion mentioned the quietness of the cabin.