Running sound card and integrated audio?

I don't really understand what you're trying to do. Are you trying to use one sound card for your speakers and another one for your headset? If you have application that let you select I/O (like ventrilo) then this certainly can be done.

Now, if you're trying to get the same audio on both the headset and the speakers, I'm pretty sure you'll need some kind of spiltter adapter.

This is my plan,

connect speakers and 5.1 headset to my sound card.

Then use integrated when connecting to home theater. Realtek HD has Coaxial surprisingly.

That should work, you'd just have to switch the default sound device in control panel>sound if your not able to select different devices in the software your using.

so i dont have to uninstall realtek like when i have to uninstall ati when installing nvidia?

It can be a bit hit and miss as far as conflicts I think, I've had an ExtremeGamer and Realtek running on an Asus P5DH but I've seen it not work for people.