Help a noob out with his PSW505

Hello friends,

I am inexperienced and do not know how to properly connect my subwoofer to my PC. I think this because I've used line-in speaker cable to connect to my subwoofer port on my sound card and I don't get anything when I play music. I'm under the impression that I'm simply using the wrong cables, and not properly connecting my system up. I would much appreciate some simple assistance and guidance on which exact cables to buy to get my setup producing sound.

What I have:

Xonar D1/A Low Profile PCI
http://www.newegg.com/Product/Product.aspx?Item=N82E16829132007

PSW505
http://www.newegg.com/Product/Product.aspx?Item=N82E16882290130

Sony HTXT1
https://www.amazon.com/gp/product/B00IWQREOE/ref=od_aui_detailpages01?ie=UTF8&psc=1

What I've tried:

I connect regular old PC speaker cable to the "Front" port on sound card to the HTXT1 analog port. This gets me sound.

I connect PC speaker cable to the LFE IN port on the PSW505 to the "subwoofer/center" port on the sound card. This gets me a regular hum/buzz that I can make louder or softer using the volume control on the subwoofer. It does not change when I play music.

I connect RCA cable, Left and Right, to the LINE IN port on the PSW505. I take a RCA-Y adapter, RCA Female to PC speaker Female, and plug a PC speaker cable into the adapter and the other end into the "subwoofer/center" port on the sound card. This gets me no sound on the subwoofer, even if I raise the volume or mess with any of the dials or switches on the back of the subwoofer.

My PC runs Windows XP, I have the latest drivers for the sound card installed.

What I want:
I want to have music play out of the HT-XT1 (with the bass possibly turned all the way down) and have the subwoofer bass accompany that music, so that both devices are working in tandem to produce sound.

What cables should I be using to achieve my end goal?

How they should be connected in my system?

Thank you for reading