Newer Modems/ # of Channels that modem can bind

I was frustrated with my internet speed on Cox in Rhode Island.  I have been on the Ultimate tier for 3 years.  With an old Cisco Docsis 3.0  modem that binds x4 channels that rented from Cox.   Reading Cox's own recommended router page they say the minimum is 16x4 for the Ultimate service.  Would have been nice to know this-  since Cox knew both what tier I was on and that they were providing me with an unsuitable modem.

Well enough.

I bought new DOCSIS 3.0 24x8 modem, Cox support was good about getting it set up.  I am getting most of the 150M speed I am paying for, MUCH better than the old speed.  Since I'm in a Cox only area, all my neighbors are on, and in primetime it still gets slower than 150, but my test at the moment says 130M- good enough.   I understand that by binding more channels the modem gets more throughput, I want to grab all the channels I can.

In my router stats, I see I am only binding 12 channels.  My question is how many channels am I suppose to be getting on the Ultimate tier, how many are available on lower tiers.  And is there some way I can further optimize my connection?  Can I request that more channels are made available to bind with?

thx.