I have an S2 as well. Although, I do recall having listened to the original DIN input (and later RCA input) CAS4040, that was via dealer dems a few decades ago now. I do remember greatly preferring the Creek over the NAD 3020, which was the closest market competitor at the time (along with the Rotel RA820 which that dealer didn't carry). When a minty S2 landed on the dealers used shelves some 10 years ago now, I just couldn't resist adding it to my collection of 'The Little Amps That Could'.
I don't recall having had a listen to an S3, however, I do remember the dealer saying that Creek had finally got round to suppressing the turn-on thump.
The link below will get you a copies of the 4040/4140 S1 manual and an S3 brochure direct from Creek.
https://www.creekaudio.com/archive/4040.zip
I have some other versions of the manuals at home if you'd like more.