I found a 105 5800 equipped S2 at a great deal, so I picked that up. Added some 60mm profile carbon tubulars, and love it. The S2 accepts 25mm tires, where the 2014 S5 I was looking at did not, so I went the S2 route for the added comfort. I'll add the dual position seat post next summer, once triathlon season starts.
I didn't see this on time- would have loved to do this. How was it?