+1 on the Bern helmet with the winter liner. It has to be below 30, though, or it's just too much. There are two retainer loops on the ear flaps. If you pass the chin strap on the outside of the loops, the ear flaps fit looser and you get a little wind passing through and the ventilation is good for, say 25-30 degrees. If you pass the chin strap through the loops, the flaps fit tighter and give you protection in colder temps.

Unfortunately, my Giro 100 Proof gloves are only rated down to 16 degrees, though that's pretty optimistic on Giro's part and doesn't take into account wind chill on a bike moving 20mph...