Hardware :: How To Configure Router/Modem

So, for the past 5 months or so, any time I'm using the internet at home, the connection speeds are atrocious. I bought a new modem (which Charter quickly dispatched as being "unsupported", despite 3 techs telling me it would work), tried hard wiring my iMac to check for wifi issues, and have basically just gone out of my mind with speeds that make dial-up look favorable.

Whenever I experience page timeouts or flat out no connectivity, I resort to the time-tested "turn Airport off/on" solution, which provides a page or two of fast connectivity before the slow downs continue. I'm beginning to think my router is on its way out, but the fact that it works sometimes makes me think it still might be the ISP.