Agreed with KirkeIsWaiting. You may wish to go with a size or a half size a little bit larger. Unfortunately, you just missed Nashbar's sale on shoes a few weeks ago; but if you like the colors and whatnot, the reduced price seems like a reasonable deal.
You may also wish to consider a pair of Cannondales since they are just rebranded Diadoras. I own a pair of Cannondale RP2000 (no tongue) and RP2100 (with tongue). I believe with the RP2000 style design, the tighter fit has to do with the fact there's no tongue and a more pointed toe. Just as a reference, I found the RP2100 to be closer to the fit of Sidi Dominator Lorica 5. For me, the RP2000 is a half size smaller than the RP2100.