No need for a cable box, much less cable TV (or home phone service as well)
You just need a internet connection, then install XBMC on the laptop, then install XBMCHub wizard.
As for ditching cable TV so you are not burdened with that $100 charge each month or more, then pick up Pivos to load load Linux XBMC (and HUb) and drive the TV from it.
Note, you can just drive the TV from the lap top, but this requires that the laptop be on when you want to watch TV, and where the pivos box come in instead.
As for downloading from with XBMC, you can always do so, but no reason since what every you want to watch, it just a few clicks aways.
And to one better, if you need a land line phone in the house, then add an OBI box goes for $40, and you can tie it into providers such as Google voice for free.
Simple, we are in the age that all you need is just a basic internet connection in the house ($19.99), and the rest is a snap that you don't need to pay someone services that you can configure through the basic internet connection at your home instead.