This is for people wanting more instances at higher sample rates. Without the expansion card, the number or instances of the Liquid Mix software (maximum number of channels that can be processed simultaneously) reduces as the sample rate doubles, e.g. 8 @ 88.2/96kHz and 2 @ 176.4/192kHz. With the expansion card, this number doubles to 16 @ 88.2/96kHz and 4 @ 176.4/192kHz.