I assume they have DOCSIS 3.0 (D3) in your area? You might be able to go down a tier and invest in a D3 modem? Have you been a cox customer long? Maybe talk to their loyalty department and see if you can sign up for a service contract. If Cox is the only decent ISP in the area then at least get something back for sticking with them.
They do have DOCSIS 3.0 service in my area. I have been a Cox HSI customer since 2010. I can't sign a contract being that I won't be living in the current residence for long, I will be buying a house soon.