IP35 Pro S/PDIF Passthrough Question

[Professorblinks]

Hey all,

I have a Abit IP35 Pro running with Windows Vista 64. I have an Xbox 360 and a set of Logitech Z5500. I currently am using the onboard S/PDIF outputs to do 5.1. The Xbox 360 also has an optical out. I am currently set up:

XBox Optical out -> IP35 Optical In -> IP35 Optical Out -> Logitech Z5500

This setup works great except I have one complaint. When I was using the passthrough with 3.5mm jacks it would "combine" the two sounds. I would not have to switch the passthrough on and off in the computer. I could be playing the Xbox and listening to music on the computer at the same time. Now when I enable S/PDIF passthrough it does not combine the signal. It does one or the other. It now takes 5 mouse clicks to enable or disable passthrough which is a huge inconvenience.

1. Is there a way to "combine" the two audio sources in the computer?

2. Is this just a quirk of the realtek audio chipset?

3. If I purchase a soundcard will it be able to "combine" the signal?

The quality of the sound is fine for what I use it for, I am just looking for convience. Purchasing a new top-of-the-line soundcard would be just for convenience.
Thank you,
Stephen