Sound Card's and Speakers?

Hey all ,

Just in case I do buy this set up I want which includes :

http://www.ebay.co.uk/itm/ASUS-VS228H-FullHD-1080p-LED-... 3 of those in Eyefinity

Ati Radeon 6870 (If its compatible)
Speakers and a sound card

I know I would need to plug the sound card into my computer , seeing as the monitors have no sound.
So I would plug the sound card in , plug the speakers out cables into the sound card and plug the speakers power into the wall? This is correct-e-mundo , right? I sort of get confused with all these cables. I was also hoping to use one of the monitors for my xbox so I could switch it over , back and forth from xbox to pc if I needed to . This would be possible because they have HDMI which I use on my xbox?

Sorry if this is confusing.