Audi A3 2011 Cab rear speaker /chorus 2 plus help please

[den911]

Hi, i am looking at a way of keeping the oem radio cd and upgrading it so i can fit rear speakers in my 2011 Cabriolet,the car as the rear speaker grill but no speakers fitted ..What i would like help with is the chorus 2 radio and if it had provisions for 4 speakers to be fitted or would i havce to upgrade to another model ..Any help would be apreciated thanks