|In order to be able to pick up all the channels available, you often need to use a (coax) cable amplifier inline between your input cable and the TV card - they are not as tolerant of weaker signals as regular TVs are. |
Are you using a cable box (to de-scramble, if applicable) ?
If so does it have an analog coax output? Digital coax output?
Are you presently changing channels with the cable box or with the TV?
"I have a Geforce 7900 graphics card with dual monitor outputs, could I then add another monitor to serve to display the channels pulled from my tuner? "
Usually you can set the displays in the (Nvidia in this case) graphics settings so the displays are different, but I'm not sure about how to do that. Take a look in the Help for your video settings.
If the TV card has one tuner, you can only display one channel at a time. Most TV cards have a recording feature - you can only watch the channel you're recording if the card has only one tuner, or if you have one TV card with one tuner, while that channel is being recorded .
Some analog TV cards have two tuners - you can watch a different channel than the one being recorded. Or you could install two TV cards with one tuner each.
Depending on whther being able to directly input digital signals to the TV card is important to you, you don't necessarily need to get a more expensive card with that capability.
E.g. if you have digital channels, are presently changing channels on the TV, and you have a cable box with a (digital to) analog output coax connector, a cheaper analog TV card will do you fine - you'll still have your digital channels, in analog format.