I personally would not use a modem/router combo. We had nothing but problems (netgear) with ours, especially when trying to connect multiple devices.
We use the Arris 6190 modem and added a netgear nighthawk router. No issues since and we have at least 15 devices that connect to it.
Just my opinion, but if you wanted to stick with the combo, Netgear is overall a good brand. I would choose dual-band.
Whatever you choose, make sure to check against this list:
We did have an sb6141 which is rated to over 300mbps, but TW caps it at 100.