Rs3's aren't available in proper sizes for 19" M3 wheels. I would buy Yokohama AD08's in 255/35/19 and 275/35/19. It's a great tire and those are ideal sizes for ZCP wheels IMO.
'13 M3 - Silverstone II - Sold
'04 M3 - Jet Black - BBS E88, KW Clubsports