ISP SuddenLink Won't Update Firmware C6300 AC1750

I bought a Netgear cm600 this week that was firmware v,5, and they are up to v,14. It still worked on my 100mbps plan, I was getting 117 with it. Than I bought the Orbi 3000ac and upgraded my plan to 300mbps. My first speed test was 390mbps, and after that I did not pass 5; the lack of firmware fried the modem at the high speeds LOL, I took back to frys the next day. Buy ASUS l, they are good with updates, but there is a whole society of modern and router guieks with a website that offers not only free firmwares, but enhanced firm ware that unlocks things you did not pay for.