Another vote for threadless. Not really any harder to install and since you're going CF anyways you might as well take advantage of the stem availability that threadless offers.

Any stem you buy should have a shim so it'll work on a 1" fork. If not many of us probably have a shim or 2 lying around (if we also own a modern bike). I know I do.

I rode a C'dale starting in '86 and never thought the ride super harsh but I got back into riding with a college club after I decided to stop playing football and was a "bit" bigger than the average cyclist. Also my SR800 had steel forks.