"Modems rated higher than 500mbps are stuck at the Ultimate Classic tier"
False
Modems rated higher than Ultimate 500 support up to Gigablast.
"Ultimate Classic not even offered anymore"
False
Cox offers 7 plans with Ultimate Classic being a plan.
"The current tiers go from 150 mbps service to 500 mbps service"
False
The current tiers range from 25 to 940 Mbps
Stop researching the manufacturer's promise of bandwidth and concentrate on its version of DOCSIS and number of channels. If you want 1 of the top-3 tiers, get a DOCSIS 3.1.
Gigablast: 940/35 Mbps
Ultimate 500: 500/10 Mbps
Ultimate Classic 300: 300/30 Mbps
Preferred 150: 150/10 Mbps
Essential 50: 50/3 Mbps
Starter 10: 10/1 Mbps (You should get this one)
Connect2Compete: 25/3 Mbps
Cox does need to update their list of Certified Cable Modems. Cox now offers a 500 Mbps plan but it's not listed as 1 of the highest compatible package. You only see 3 packages on this page because those 3 packages are just milestones within all the plans: 150, 300 and 940 Mbps. Perhaps 500 is now a milestone but...like I said...this page needs an update.