for a 19X9.5 I probably wouldn't go with a offset less than a ET22,this would give you some flexibility to change tire brand. If you really go with the aggressive offset ala. ET19s you will probably be stuck with just the one brand so it didn't rub.
For the rears at 19X11 I probably won't go less than a ET30-33. You could run a ET25 but once again you will probably have to play with camber settings and only that one or two brands of tires that doesn't have a shoulder that will rub.
2013 M3 Coupe-MR/BLK ZCP, identical to my 2011.
2011 M3 Coupe-MR/Blk
2007 Porsche 997C2S Speed Yellow/Blk sport seats
2004 BMW M3 Imola/Blk