THe only catback I've heard that sounds so good on this car. Not fart pipe sounding but low quality refined was the Magnaflow catback. There's a thread on it somewhere around here and guys were finding it around $430 or so.
This one: http://www.ebay.com/itm/MAGNAFLOW-15...5bdd75&vxp=mtr
2012 FF Ti HB Platinum White Tricoat, Built 12/11, 401A + Parking Technology Package and MFT w/NAV at 3.5.1