Asus already announced their entry into the sound card business at the CeBit 2007. At the Computex 2007 the officially announced the ASUS Xonar D2 7.1-channel audio card.

The Asus audio card is based on the AV200 audio chip, which integrates multiple sound-enhancing technologies from Dolby and DTS to transform almost any PC into a high-quality digital home media center.
The ASUS Xonar D2 features a signal- to-noise ratio (SNR) of 118 db for both audio in and out—reaching the limit of audio quality on most PC platforms. Unlike generic sound cards in the market that provide the highest SNR to only the front stereo outputs, the Xonar D2 is able to deliver 118 db quality audio for all 7.1 channels.

Besides delivering impressive audio quality, the Xonar D2 is also packed with multiple sound technologies from Dolby and DTS to deliver outstanding entertainment experiences. These include Dolby Digital Live, which converts PC or game audio content real-time into Dolby Digital; Dolby Headphone, which creates an entertaining surround sound listening experience using any set of headphones; Dolby Virtual Speaker, which delivers a vibrant surround sound listening experience from stereo speakers and Dolby Pro Logic® IIx, which creates up to 7.1-channel surround from stereo or 5.1 sources as well as DTS Interactive for real time AC-3 encoding and DTS NEP: PC stereo to multi-channel expander.
Via this Asus press-release.