Does this motherboard support installing sound cards such as...

[ViTEO_]

http://i.imgur.com/YO7nUrV.png

is this where I should install the sound card? (circled with red)

does this motherboard support sound cards such as: ASUS Xonar DG, DGX, etc.

 

[SinxarKnights]

Modern sound cards normally use a PCIe x1 slot. Those are the short slots next to the circled one. The circled slot is a old PCI slot.

As long as there is room to fit the card, it should work. I have not tried any Asus sound cards. I always go with Creative products (only because I know what to expect and what they sound like). The Soundblaster Z is a good cheap option. It is available on the Creative website for $60 USD now.