I used to use very cheap canned tomatoes for sauce because I didn’t think it made a difference which brand I used since I was cutting corners anyway.Later I found out that not only do some cooks think canned are better anyway but that it does matter which brand.
Any reasonable supermarket will carry San Marzano. I am not lucky enough to live near a reasonable supermarket,though and most of the time end up using Del Monte. Once I’ve added a splash of Cabernet even Prego tastes better. I’m not that picky when it comes to tomato sauce and I wish I could tell you I could taste the difference between a can of San Marzano and San Luigi.