I use quite a lot of tomato puree in my sauce too

I also usually put paprika and chilli powder in my sauce, for colour, and because I find anything without a smidge of chilli in it bland these days.
My mum puts so much chilli in her shepherds pie that we used to refer to it as 'llama herders pie'.
EDIT
Recipe :
Sauce : tin plum tomatoes, oregano leaves, basil leaves, salt, pepper, sugar (a smidge), garlic, chilli powder, paprika and tomato puree till right colour, bit of balsamic, olive oil, chives finely chopped. I never bother with wine in food, but you can put a bit of whatever beer you're drinking in it

Thicken with cornflour till nice and gloopy.
Other Stuff : fry some onions till they're just starting to brown, throw in some (lots) garlic for 30 seconds or so. remove and put in a pan with chopped peeled tomatoes and some fresh basil.
Mince : Fry mince with finely chopped onion and pepper till browning, drain off the fat from the mince and add some olive oil. Leave for a while.. Add your sauce.. simmer for a while.. add your solid stuff and server with parmesan and some olives. And as suggested above, barolo!