ThunderAI wrote:
I have a Asus Crosshair Formula Z. I game and listen to music in 7.1 often. Is it worth getting an Asus dedicated sound card?

How would I compare them to the sound system in the Crosshair?

General rule? Yes. In much the same sense that a discrete video card like an AMD RX480 would be preferable to whatever embedded video card might come with a motherboard (at least, for now; when they start embedding RX480s into motherboards, they'll have a faster / better discrete card by another name).

The Xonar DSX isn't an expensive buy (~$53), but there are a lot of options, so look around, read the fine print / reviews, until you find something that makes you happy.

Additionally, some people are unhappy with the driver situation regarding Xonar cards, and have decided to patch / write their own (for more stability, IDK): http://maxedtech.com/asus-xonar-unified-drivers/