I have a modem/router combo unit provided by my ISP (Xfinity), it's an ARRIS DOCSIS 3.0 Residential Gateway with 802.11n GigaPort Router and am going to buy a separate router, likely a LINKSYS AC1900 MU-MIMO Gigabit or similar AC router with 2.4Ghz and 5.0Ghz, (Perhaps a Nighthawk, etc.) My combo unit only has 2.4Ghz. Anyhow, my question mainly is this . . . would I have the best performance by simply hooking up my new router to my old modem/router combo unit and broadcasting a separate SSID, or should I physically turn off the router functionality on my modem/router combo unit first and use the new router as my only router? Or would the difference be negligible, either way? Any advice would be greatly appreciated. Thank you.