Nope. As this page says:
- Combination Internet and Telephone modems purchased or received in new or used condition from third-party retailers are not certified for use with the Cox network.
Panoramic gateways have to come from Cox. If you want to buy your own equipment either buy a separate modem and router(I suggest) or buy a non-Panoramic gateway. Basically it can't have phone service integrated into it. If you have phone service you can get a phone modem(eMTA) from Cox for free and then you can buy your own router.