As others have said:
Competition Race - Tarmac or Allez (for 2011, the geometry is identical, just carbon vs aluminum)
Competition Endurance - Roubaix or Secteur (same thing about geometry)

At a cat 5 level, the difference between an Allez and Secteur will be negligible in terms of speed. The biggest factor is which one you can tolerate during your next century. Obviously the Secteur is more appropriate for longer distances.

Bottom line, ride both the Secteur and Allez. Which one you buy will depend on which one you can set up to fit you perfectly.