Honestly, if you're asking that type of question then more seat time is what's recommended. ...this is unpopular advise
Bingo! Unpopular, but common around these parts.
Notice the theme coming from most of the responses so far: understand what you want out of the car before you bolt on parts. The key is "understand," and that takes more than a desire to "take it to the next level." Budget, intended use, rules, and direct data (even if it's just "seat of the pants") all need to be taken into account.
You said you wanted to do "more" auto-x/track days, so does that mean you've already done some? Can you give us more info on what your experience was, what you found lacking, what you felt was working well...anything? Absent that, we're throwing darts in the dark.
We can tell you what you're likely to experience and therefore want to do, but that's about it. Stock brake pads suck for any kind of performance driving, so you'll need to upgrade those just to get out and really push the car (to get that data we're all asking for). You'll also need fresh fluid, and if you can swing it, flush the system entirely with high temp fluid. That's it. I'd even go more conservative than pcdrj and say no need to get into the stainless brake lines or brake ducts yet...again, assuming very little track experience on your part (sorry if that's mistaken, but you didn't tell us where you're coming from).
Let us know, maybe we can help.
Best,
-j