Help figuring out what I need

You use the TV tuner card that I put in the build list and record onto the 3TB HDD that I also included in the list.

Right idea. Possibly the wrong execution.

First question: Does your cable subscription require a set top box? Since you're looking at a whole home DVR, I'm guessing you do.
Second question: Does each TV have it's own cable box?
Third question: Is it possible to run computer network cables to each TV location?

byogamingpc's system build is good, but some components may be wrong for your purposes. The TV Tuner card s/he lists is only for free over-the-air (OTA) broadcasts and cable signals sent in the clear or ClearQAM. If your current subscription requires the use of cable set top boxes, that TV Tuner card will not give you all the channels you subscribe to. Only a cablecard ready device will do that.

To my knowledge, there are only a few cablecard ready devices available on the market still:

Ceton InfiniTV4 PCI-E - Internal Quad-Tuner device (also what I use)
Ceton InfiniTV4 USB - External Quad-Tuner Device
SiliconDust HDHomeRun Prime - External Tri-Tuner Device
Hauppauge WinTV-DCR-2650 - External Dual-Tuner Device

Any of these would work as a whole home DVR, In general, you'd need one cablecard leased from your cable company (in my area the first one is free, each additional is $2/month) rather than three set top boxes (in my area, the first one is free, each additional one is $18/month). Of course, if you go with either the Tri- or Quad-tuner device, you'd only need one cablecard.

The problem here is that most people do not have their homes hard-wired for computer networking and these devices do not work over wireless networks (therefore byogamingpc's wireless card is unnecessary). For these homes, there is MoCA or Media over Coaxial Alliance. A MoCA network allows you to run what is essentially a home network over the existing coaxial network within your home. However, since I was able to hard wire a computer network through my small apartment, I have no experience with MoCA networks.

The last piece of the puzzle are media extenders. These are the devices that connect your HDTV to your media network. Surprise, surprise, you already have one in your XBox. Another option is the Ceton Echo (combo linked). With a media extender located at each HDTV that is not directly connected to the HTPC, you can assign individual tuners from your Tri- or Quad-tuner device to these extenders. Once assigned, each HDTV believes and operates as if it has a set top DVR attached. Using the Ceton Echo remote or the XBox media extender app, you can watch live/recorded TV at any attached device. You can set up recordings at any device.

So, looking at byogamingpc's build, you could scrap the wireless adapter and the tuner card (I'd probably drop that power supply as well) and add in the Ceton InfiniTV4 PCI-E card and something like a 400 watt PSU from Antec, Seasonic, PC Power and Cooling or Corsair. Since the bedroom TV is the only device that doesn't have Netflix/hulu apps, I'd recommend connecting the HTPC to that TV.

-Wolf sends