christopher, the reason you are not happy with the cento tomatoes you are buying is that they suck. The only good cento product says Italian tomatoes, not italian style tomatoes, or filets, or anything else. Italan "style" are really bad. When you find the right can I predict that you will be happy with your sauce. These tomatoes are so good (thank you jeffery V!) that they need no herbs or spices. If you get right amount of salt in there, and get them thick enough you should be totally happy. Once you have achieved this you can then start messing around with tiny amounts of oregano, garlic, pepper, sugar, or whatever else you like to spike your sauce with. I find no need to do this.
P.S. even the DOP san marzano's are not as good as the cento Italian.