The auxiliary input is meant for a specific voltage level such as you might find on headphone outputs. I'm not certain about the TV. Even if you had something like an RCA->3.5mm adapter the voltage might be wrong.
The second issue is what you want to do with the sound. I'm not certain but I think the input on this and most (all?) audio cards is meant for recording, not for playback.
I see no reason to record audio from a TV but not video so I'm assuming it's for playback. If that's the cause (and the voltage levels were okay) then you'd be better off getting a splitter and putting the sound directly into your speakers.
I doubt any of that's really going to work.
While I don't quite get the point of what you're doing, my only suggestion would be to get a Receiver but that gets expensive.
Tuner cards are another option, but you'd be much better off getting a recorder from your TV provider. My satellite box wasn't the top model and has no internal hard drive but I can add my own via USB.