I don't see a problem with using a puree at all, if tomatoes aren't in season they aren't going to have anywhere near the flavor of their canned counterparts. Canned tomatoes are picked when they are perfectly ripe. I use puree as well, but check the label since many of them also include tomato paste in them (which is good, makes a richer sauce), but if they don't I will add some tomato paste to thicken it up. I generally make my pizza sauce a little spicier with some extra oregano and red pepper flakes. It needs some heat and tang to offset the creaminess and richness from the cheese.