I don't know what a break disc is.
I do know what a brake disc is, though.
The question is what are you trying to accomplish? A big brake kit? More performance, better stopping power? The stock brakes are more than adequate for normal driving, even spirited driving. Remember, the limiting factor is your tires grip on the road, not the size of the rotors. The only advantage if a bigger brake kit, is resistance to brake fade, due to better heat dissipation, and being able to perform under higher temperatures. That being said, if you do change the size of the rotor, yes, you will need new calipers. I don't know if there are any direct bolt on kits for the E90. There are several vendors that sponsor this forum, and may be able to assist you in finding a kit. However, if you just want to change the look, many people opt to paint their brake calipers with a high temperature lacquer paint that will look better than the cast metal color of the factory calipers.
ASE and BMW Master Certified Technician
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