Is your motor basically stock?
If so,
1973914 nailed it. Rebuild your stock calipers and use awesome pads. Yup they'll cost you a hoot but it beats mess'n with the current setup. When they work they work better than most any set-up for a stock/semi-stock car. And yes... "all" drilled rotors (cast or drilled) crack. No biggy, they just do.
If you have a high hp motor then by all means look at upgrading your system. I wouldn't consider the BMW's an upgrade, simply more pad without addressing "system" issues. Others have covered what it means to have more heat on the same old rotor, especially in an auto-x situation. "System" means, front, back, p-valve, calipers and rotors.
E.G.: I went up to a six. For me this meant S-calipers, vented rotors all around, t-adapter in place of the p-valve, 911 rear calipers and 911 handbrake. Boatload of work and $!
Short answer: rebuild your stock system with nice pads. You'll have more cash in your pocket and an awesome brake system.