Upgraded to 100mbs only getting 40mbs

I upgraded to 100 mbs. After a few speed tests I'm lucky to get 40mbs over wifi. I know with wifi you will lose some speed, but 10-15mbs is reasonable. 60mbs is not. 

I called support and they said since I do not have an ethernet port they cannot do anything to help me figure out why. It's 2017 and a lot of computers, specifically macs, don't have ethernet anymore. Is there anything I can do? I'm in the same room as my router and nothing is working. I own my own router, it's a Motorola SBG6580. It's not the best, but the specs of this should be MORE then enough. Support wouldn't recommend a SINGLE action for me to take. I'd ask questions and nothing. Nothing we can do because you don't have an ethernet port... You are kidding... BS. 

Is there a better modem/router I can get? 

I really wish an other option was available. But COX is unfortunately the only provider... They and their support ***.