The question of latency reduction when using Live Preview mode (Live Feedthrough Mode) occasionally comes up, especially in broadcast applications. Although counter-intuitive, use the highest possible sample rate that your system will support (along with Direct X WDM drivers) to minimize latency time. 16 bits is also recommended. Generally, that means using a sample rate of 96 kHz or 192 kHz depending on what your system supports.
Craig
Craig