I have Xfinity cable triple play. I recently purchased an MT7711 modem/router/voice to avoid rental fees. My wife added “gigabit extra” which I believe gives me 1200 mbps download speed. Xfinity now says my router can’t handle those speeds and the only replacement I can find is around $300. 1- do I need 1200 mbps if I only use internet for tv and surfing? 2- can I pair my MT 7711 with a MB8611 or do I have to find one on unit modem/router/voice? I hate to get rid of a fairly new MT771 if I don’t have to.