Few new PCs come with TV tuners built in, but you can buy them and plug them into expansion slots. The Dell Inspiron 660 series would fill the bill nicely. Looking at the Dell web site at
http://www.dell.com/us/p/desktops?~ck=mn I see prices start at $279, and you can customize them to suit your preferences.
Just cut cable tv, and am looking for a desktop pc I can watch through my hdtv, for $500 or under if possible, just got roku 3, any advice greatly appreciated!!