[acid_rider]

also try Cervelo RS

I would be a size 51 in the R3.

Are you a size small in the Look? Look forward to your Ultra impressions. Some good 07 deals out there.

Something else to consider: (keeping in mind what C-40 said).

Cervelo RS is very close to R3 geometry (same STA and HTA and main tube lengths) but with 10mm longer rear chain stays and a 20mm taller headtube. So in a 51cm size the RS might offer a better geometry that 51cm R3 would.