The most important thing is to strain the seeds out. They're what makes the sauce bitter.

Actually, I've bought Redpack on sale. They're not bad, although I too prefer Tuttorosso. Rienzi's also pretty good, too.

I personally don't add my sugar until the very end. I would rather let it cook for a few hours. Also, the meat that you add determines the flavor of your sauce. If you like spicy gravy, then put in hot sausage. I prefer a sweet sauce, so I usually add piece of pork and one of chicken. Just make sure to brown them before adding them to the tomatoes.