You need to address what type of usage your brakes will undergo. Until that's clear, any advice is pretty useless.

When you say 'drag racing', I'm assuming you mean that you want to be able to stop once, very quickly, from a high speed, and then you probably won't use them again for a while. In that case, your best bet is to just invest in some good pads, make sure your system is calibrated and tuned, and get yourself some sticky tires and better suspension. Most people don't realize that 50% of your braking effectiveness comes from tires and suspension. The OEM rotors and even rear drums are fine if they're in good working order.

If you're talking about something like AutoX, where you'll be constantly on the brakes, like maybe repeated 120-80 stops, then you need something different. If that's the case, then you'll want to look at maybe drilled rotors, definitely better pads, some different fluid that stands up to temperature better, etc.

Don't get me wrong. A huge rotors and four-piston calipers will always help, I'm just saying that if all you're doing is the odd quick stop, there are other options that will be 90% as effective, and about 25% of the cost.