I am running the latest version of The Witcher (1.31) and the latest NVIDIA drivers (376.33) with 2 GTX 980ti in SLI. I am using an ASUS Xonar U3 USB audio device to convert the in-game audio to DD live over optical. With SLI disabled, there are no issues at all. However with SLI enabled, the in game audio skips and drops out constantly. Both GPUs are nearly 100% utilized and I am getting between 80-120 fps running at 2560x1440 . The PC specs are:

Intel Xeon x5670 @4.1 GHz
x58 motherboard (x16 + x8 PCI-E)
12 GB RAM

other games do not have this audio problem. Are there any settings I can check to optimize the game for SLI that may be leading to these issues?

Thanks in advance for any input!