I recently purchased internet from my isp Cox "prefered plan" and i decidef to buy the dual band netgear n900 which is a cable modem and wirelesd device in one from cox. The problem is that when i got everything set up and hardwired my pc to the wireless router and attempted to play an online game called combat arms i would get a really unstable connection. I would go from 3 ping to 2 and sometimes 1 ping in a mater of minutes. Than i decided to cannect my old cable modem and the lagg and unstable connection disappeared. I would Also lagg when connected threw the wireless routers gigabit port even when i was the only one connected to it. Could it be the router or are hardwired connections less stable when connected though a wirelesd router. I was thinking of buying the Asus RT N66U, but not sure if i would have the same ploblem when running the game from its gigabit ports..
ISP bundle appliances are notorious for being buggy and low quality. Your experience is far from unusual. I would recommend using your stand-alone modem and the RT N66U.
I actually got that exact same router for my parents and their network works pretty efficient. My brother who still lives at home games online (both Xbox 360 and PC Gaming), my parents use their computers constantly for work, and its range reaches all three floors without extenders. I wanted wireless AC because I do a lot of media streaming throughout my home, or I would have opted for the N66U easily.
They have ~15 wireless devices in the household and this router does the job for them quite well.