Dunlop0078 :
Your ISP didn't give you one? If they did that should be fine. If they didn't I wouldn't suggest an all in one, I would get a decent DOCSIS 3 modem maybe an Arris surfboard SB6183 and a good router at least wireless N but personally if I was buying a router in 2016 going on 2017 it would be wireless AC, however those can be pricey.
They do provide one, with a $10 rental fee. So just makes more sense to buy.
Are there many benefits with getting a modem and a router as opposed to a 2 in 1? The ARRIS SURFboard SBG6580 just seemed appealing to its $30 refurb price tag. Though I dont think it has the 5ghz capability for wireless.