From all the factory pans I've seen I'd go with a 06+ STI version pan. It will give you more header options and compared to the previous STi versions it's a better pan. The 06+ pan has the drain plug lower (so more oil drains out on oil changes), and if you want to get every drop out (with a hose and pump) or peek inside it doesn't have a shroud over the drain hole. I'd say the baffling is probably marginally better too. The only thing I don't like about the 06+ setup is the pickup sits a little too high for my taste. Since I run my own pickup I don't have this problem because it sits a little lower.