As far as ATT Uverse, their “Wifi gateway” is likely just a DSL modem. Can you get any old Verizon/Westell unit, put in the correct authentication info and return their device?
Re: Time Warner. If I go to their site and put in a San Diego address, they’re now ONLY showing the 100 Mbps package for new subscriptions. $40/mo with or without modem rental. They charge extra for WiFi for some dumb reason though, even though routers are about $40.
Did they upgrade everyone to 100, and why is 300 not available?