For the classic/cliché pizzeria sauce flavor...buy "6-in-1" brand 
ground tomatos in a can.
Speaking of slow-rising, try taking some of the total amount of flour 
and making a Poolish with it. Let the Poolish sit out 12-15 hours 
before making the dough. Really adds to the dough's flavor and 
extensibility (which is so useful for pizza!.
Allen Cohn
Home baker
San Francisco
PS: Pizza dough is one of the few times you'll want to use traditional
active dry yeast instead of instant yeast. Active dry yeast has a 
chemical in it that aids extensibility.