After riding my Roubaix, I was throwing rocks at my aluminum Secteur. Roubaix has 25's, Secteur has 32's and the Roubaix is by far the smoother bike.
I'm in the 265 range and ride carbon as well. 1,700 miles so far, no asplosions.
I rode with a big guy the other day that has his Roubaix loaded down with Randonneering (sic?) paraphernalia. He said he is notorious for breaking bikes and hasn't been able to break his Roubiax's. He has two and rides them in those 400 mile/24 hours deals.