If you have a SB6183 running slower with just 4 channels (seen at http://192.168.100.1) you can get full speed and 8 channels back

See also (locked) thread:
Only getting max download of 33 Mbps with new DOCSIS 3 Motorola SB6183 16channel modem and Premier upgrade

It took over a week to get to the right folks in support, but eventually the above forum post, mentioned to the @CoxHelp person I was Twitter DM'ing, made all the difference.

See also:
TinkerTry.com/sb6183

Hoping this forum post can help avoid some early adopter pains for other Cox customers who bought a SB6183. Let's hope they add the self-install menu option for this modem soon, so that proper provisioning would be painless.