Buy the absolute best brakes you can afford. Two-piece discs will save you weight at the exact place you need to be saving it, so a 1KG saving there is worth a 5KG saving anywhere else on the car (it's why light wheels are worth a fortune!). I would consider any extra cost very much money well spent.
I used the PF two-piece discs on mine and they were absolutely immense, however the DBAs would be my next choice if the PFs weren't available. Get the brake hoses done as well if you haven't already done so while you're there (very little extra labour needed) and some good fluid in there and it will make a huge difference to the car as a whole. If you can stop quicker then you can go quicker, and if you weigh less you can corner faster.