What you have is more than enough to get on the track
Frankly, I like to keep it reliable to maximize track time versus repair time, so I kept motor mods to bolt ons, but made a lot of other mods with the goal of reducing weight. Motor: CAI, headers, cat delete, exhaust, GAIC program and underdrive crank pulley. As for suspension: JIC coilovers, GT3 front sway, H&R rear sway, drop links, stock brakes with Pagid black pads, ATE fluid, SS lines (not worth it, btw), GT3 brake ducts, BBS LM w/ Nitto NT01 and spacers as needed. Other stuff: carbon fiber hood, CF hard top and CF GT3-style front bumper (and just for style CF side mirrors and side air ducts). Cut out the rear bumper on either side of license plate to let out the hot air. Removed the carpet, center console, convertible mechanism, spoiler mechanism, rear bumper reinforcement, and front trunk carpet and trim. Installed 11 lb battery, kevlar Cobra seats, 6 point harnesses, 6 point bolt in cage, B&M short shift. And I just raised the wing 2.5 inches to get cleaner air.
Anyway, based on what you already have, I'd just upgrade brake pads, fluid and maybe add the GT3 brake ducts (they're only $30 from suncoast
http://e-partssales.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=P&Product_Code=airducts&Category_Code=986boxsters and take 20 minutes to install). With that setup, I've never had problems with the stock brakes with the right pads and fresh fluid. And that includes running Buttonwillow #18 CW, which includes braking hard from 138 mph for a 2nd gear turn.