2) For OTA, a nice ATSC tuner card would work. For cable, you'd need a box with firewire output to pass HD into the PC. No current sat boxes can be hooked up to a PC via HD at all, some very older models can be modded to add a firewire or USB port but it's costly ($500+) and the Directv receivers are going to be obsolete at some point.
Basically if you plan to view via a cable box or sat box, get yourself a TV that has enough inputs that you can attach your PC to it and also the cable/sat STB.
Basically if you plan to view via a cable box or sat box, get yourself a TV that has enough inputs that you can attach your PC to it and also the cable/sat STB.