Well, the rotors have been the same size from the 99RS all the way to 04+...so you can get any RS-sized rotor form those years.
Fortunately, you have the same Calipers as the WRX, but the true test to braking performance is the size of the rotor and the pad material.
I personally would suggest WRX rotors (Im doing the 02RS - WRX brake swap soon myself) and some good pads. Nothing is going to get rid of the brake gap other than larger rotors.
I would NOT reccomend getting "slotted/cross drilled" rotors as they tend to warp and crack. Ill take pics, but to do with RS - WRX brake swap, you just take off the parts from the RS, and put on the parts from the WRX, no disconnecting calipers or anything, its just a simple piece of metal that gets replaced.
Here is the piece you replace with the swap (along with the rotors).
PM me if you have any more questions.