THX Onyx: A do-it-all DAC for the travelling audiophile • The Register
Sound Blaster X3 - Hi-Res 7.1 Discrete External USB DAC and Amp Sound Card with Super X-Fi for PC and Mac - Creative Labs (United States)
Sound Blaster X7 - Desktop USB DAC and Audio Amplifier - Creative Labs (United States)
Creative Sound Blaster X3 Hi-Res External USB DAC and Amp Sound Card with Super X-Fi Holographic Audio, 7.1 Discrete Surround and Dolby Digital Live with Line-in and Optical-Out for PC and Mac :
StarTech.com USB Stereo Audio Adapter External Sound Card w/ SPDIF Digital - ICUSBAUDIO2D - Amplifiers & Voice Recorders - CDW.com
Emotiva Big Ego USB DAC Review - HomeTheaterHifi.com