the main board just has a couple of AES and analog on DB-25 connectors, then as an option, you can sell an I/O box that does all the digital conversion, firewire bridge, EXPRESSCARD link, PCI-e link, etc... and offers analog port breakouts to XLR. This box could be bolted with...
http://www.bitsavers.org/components/harris/1991_DB301.1_Harris_Data_Acquisition.pdf