The Turtle Beach Audio Advantage SRM is a small-form factor external sound card capable of 5.1 or 7.1 surround sound. It is the flagship model of the Audio Advantage line, and, as such, is the only model to support surround sound. It is also more expensive than the step-down models at $79.95, whereas the Amigo retails for $39.95 and the Micro retails for $29.95.