Rear subwoofer

I have 2000 cadillac deville. The rear subwoofer is blown. I called the dealer and was told it was 398.00 for the replacement. The speaker is made by Delco I was told. It is a 10 in. dual cone 4 ohm subwoofer and a stock part. I tried to find it on the internet but could not find it anywere. I refuse to pay 400.00 for one cheesey looking speaker. I replaced it with another fosgate but not the same sound. I have the part # 16246789. Found it on one sight on the internet but they don't carry it anymore. NEED HELP