LeeB,
You might want to check again on the origin of the Cento tomatoes. If they are the ones in the can with the yellow label, I am fairly certain they are imported from Italy. You usually have to get on your hands and knees on the floor of the supermarket to find them. The Cento tomatoes can be San Marzanos, including the DOPs. My daughter-in-law tried the Cento DOP San Marzano tomatoes and said they were good. I believe Jeff Varasano also uses the Centos, but I don't know what specific tomatoes he uses. It could be something other than the San Marzanos.
Peter