HTPC with no reciever?

I will be buying an HTPC for all media, I have a set of 7.1 Onkyo speakers with no receiver, I would like to power the speakers directly from the PC and still be able to get quality sound. I will also have a few game consoles, I would like to be able to use the HTPC as a "receiver" to control the audio for everything else, is this practical? what are my options for making this happen?

You would still need an amp or better yet an integrated amp.

can I put an integrated amp in any pc or are there only certain motherboards that support it?

It is an outboard device, like a receiver without the tuner. The audio from the computer must be amplified somehow.