Are you replacing the brakes on your e46? Probably okay just to replace with OEM parts. Are you racing the car or doing anything intensive? If you are you can probably get away with changing to a more aggressive brake pad.
Best choice is Brembo Gran Turismo big brake kit, at least in the front. If you are running stock go 4 piston calipers, if you are supercharged or other substantial engine enhancements I would go with 6 pistons. I like slotted rotors but cross-drilled are great too.