I've owned a SBLive! an MX300, and now a Turtle Beach Santa Cruz, and I'm going to guarantee something...
Those recommending the SBLive! for audio gaming quality, have never experienced the Santa Cruz. The Santa Cruz is a much, much better card, ESPECIALLY for gaming. Since it's not available OEM, it'll cost close to $100. But it is so worth it.
The A3D cards are a whole lot better for gaming too, but I can understand not recommending those due to Aureal's uncertainness.