I am going to add Sirius Radio and was wondering if there are auxiliary inputs on the system that came with the car (2005 GTO).

Umm, no. There is an input for Bluetooth, but it is mono. There are some guys who have figured out a hack that requires removing the radio and sodering wires onto the circiut board for the input. This gets Aux in on the CD palyer, but requires a burning a "blank" CD so there is no CD signal playing over the AUX. Check out this thread for their effort/solution. It's a fun read.

http://www.ls1gto.com/forums/showthread.php?t=33445&highlight=xm

Ok I'm not at home to grab my owners manual, where is the input and what do I need to get it up and running? Thx!

http://www.cartoys.com/Default.cfm/p/Motorola_Deluxe_Bluetooth_Car_Kit_HF850/

http://www.cartoys.com/Default.cfm/p/Parrot_CK3100_Bluetooth_Car_Kit/

Found these nice little blings. Probably go with the latter, it has a dispay. Its looking more and more,(here) that they will make talking on cell phones illegal, while your driving. Unless its handsfree. Some people just can't multi-task.