Sound like the woofer has been knocked out of alignment. SVS should be able to take care of you there. The platform they use for that sub is the Peerless XXLS 12". If for some reason they don't carry that driver in stock, you can always buy one elsewhere.
Here is the 4-ohm version and
here is the 8-ohm version. My guess is that SVS uses a 4-ohm driver, but sometimes it says on the driver itself, so you can just remove it and look for yourself.