Why are you interested in changing them? Nothing wrong with the stock equipment for any street driving, invest in some good brake pads and high quality fluid and you won't experience any fade.
4 pot brake fit is a very good setup, for fast road-track use its worth it, pads, disks, lines, fluid and master cylinder stopper is going to cost over the £200 mark, If that was me i would put the extra £400 and get the 4 pot brake kit