Preferred modems?

Here is a list of Cox compatible devices.  Everything listed under "Additional Cox Recommended Devices" will work and be DOCSIS 3.0. Anything marked "Ultimate" to the right means the modem has 8 downstream channels instead of 4. Usually modems with less channels cost less, but if you have the higher tier (Ultimate) then you need the better modems.

If you want to future proof yourself I would say go with the SB641 though wait a week or two. Its been going on/off Sale on Newegg and Amazon for about a month. You can find it on sale for 70$ which is a great deal.

Regarding the SB6141, there are Motorola and then there are ARRIS/Motorola versions of this modem. As I understand it, ARRIS bought out the Motorola line of modems, so which is which and what is the difference between the black Motorola version and the white ARRIS/Motorola version. Surely Cox should be able to tell us what the difference is and which is better for their customer.

Get the white one. The black SB6141 were made exclusively for Comcast customers. While they still may work, they are either 2nd hand...or "fell of a truck". But hardware wise, they are exactly the same.

Also, try to stay away from sites like Ebay and other reselling sites. Even though the deals are tempting, I find 2nd hand modems to be more trouble then they are worth.