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.
'08 E90 M3 - Alpine White - Sold
'13 E92 M3 - Silverstone II - Sold
'04 E46 M3 - Jet Black - BBS E88, KW Clubsports, Brembo BBK, SuperSprint Exhaust, Recaro
'15 i3 - Laurel Gray - Why would I mod this thing?