I sounds like you want to capture the Cable box signal and record it to your computer. Therefore you will need a "capture device/card".
As you will see from other posts in this forum, JRiver is working on getting the Hauppage Colossus capture card working. The Coloussus is an internal card. Hauppauge also makes an external capture device (the HD PVR
http://www.hauppauge.com/site/products/prods.html) which seems to have less problems. I'm confiedent the the Colossus will be trouble free soon if you want an internal card.
The JRiver Television setup will provide guide data from your Cable company based on zipcode. You will be able to use the JRiver program to select what to watch and record from within MediaCenter. You will need MC version 17 (latest version).
The Harmony will work with JRiver and the Cable box, but you will need an IR transmitter to send the signal to the cable box for unattended recordings. The Media Center remote shown in upper right corner (sold through JRiver) works great (just use your Harmony one in palce of the remote that comes with the receiver/transmitter).