Geez.
I have a audigy 1.
Personally I use the SPDIF out, which is great. It's unfortunate that your receiver can't support it.
Look heres the dope:
(for the sake of making this easy to explain)
The "top" is the part of the PCI sheild that is bent and were the screw goes in.
The "bottom" is the firewire port.
The bottom-most plug is the "rear out" jack.
The next up is the "line out" jack. That's the normal stereo/headphone/to-amp out.
Those 2 jacks make up the Four main speaker. 2 front, 2 rear speakers.
The next up, the middle jack is the Mic input.
The second to the top the Line in.
Now the TOP is special. It's dual purpose. It's called the "Analog/Digital Out jack"
It's for spdif AND center AND subwoofer.
So what you end up with the analog 5.1 setup is this:
1 channel for left.
1 channel for right.
1 channel for left rear.
1 channel for right rear.
(and for the complete 5.1 setup.)
1 channel for center.
1 channel for subwoofer.
The subwoofer is also sometimes called "LFE" for low frequency effects output.
You see when set to analog mode the Analog/digital ouput jack carries the Center channel on the "left" side, and the subwoofer channel on the "right" side.
So if you have a mini-jack to RCA stereo splitter then your white plug will be the center channel, and the red plug will be the subwoofer/LFE channel.
That way you end up with 5.1 different channels. 2 front, 2 rear, and 1 center and .1 for LFE.
Also if you ever get a reciever that has a single "DVD input" (like mine, it's orange) that's the RCA form of the SPDIF connector, in that case when you set the card to digital output mode then the white side of the plug is the channel carrying the digital data, and the red side doesn't do squat.
All this can be found out in a PDF files on the creative website, so you can download them for future reference.
It took me forever to figure this stuff out...
I hope it helps you.