Am I really going to be the first to recommend the Cervelo? This place has really gone the way of the Cannondale. Don't get me wrong, I have tons of respect for both companies, and would happily buy either one if I was shopping. I think they fit different categories of bikes though. The Cannondale is simple, understated and classy, is surely a wonderful bike, but it's not going to turn to many heads out on the road. The S2 is just straight nasty (in a very good way). It's the race-car version of the roadbike, will certainly have at least the stiffness of the SS, and will look far more at home while riding >25 mph. Perhaps a negative to riding the Cervelo is that it might hold you to a higher standard of performance. This could be a good thing, pushing you to meet the challenge, or embarrassing if you can only hit 25-30 while descending. =) I personally would prefer the ultegra over rival, but I'm probably in the minority around here on that point also.

So my final answer? Don't buy either if you don't have the money...but if you do have it, choose the one that fits your cycling style the best. My vote says Cervelo, simply because it's an amazing looking frame with rock solid componets, but if you're more of an understated cyclist and really want sram, then go with the SS. Either way, you'll be able to realistically expect to get exactly 1 day worth of performance increase before you're going exactly the same speed that you're achieving now on your Caad9. You'll just have a wider smile on your face.

-Jeremy