Have you ever considered doing that wall-outlet-networking stuff that goes on? It essentially turns all your wall-plugs into ethernet/wired lines. The cablemodem feeds it to a plugin device that energizes the rest of your house with internet through the power lines. You plug in a dongle of sorts into an outlet and jack your wifi/wired into that.

this stuff (I just googled, linked the first product - search around more for different/better/worse devices):

http://www.amazon.com/Netgear-85Mbps-Powerline-Network-Adapter/dp/B001AZUTCS

I've considered trying that, and I remember a few years back some energy companies were looking to get into the ISP game by feeding the internet over power lines, too.