But I know of one or two that have got some PC USB cards to work on there Mediator boards.
But what make and chip set are they ?
I can only speak for Prometheus users, and (with the firmware upgrade being available) I can only recommend NEC USB2 cards.
They are a few EUR more expensive than the cheaper VIA or ALi chipsets, but usually work more reliable. Avoid VIA and ALI, they tend to make troubles, I never got them working stable in Prometheus.
I have several NEC cards here from testing, from different manufacturers, but no difference is noticeable.
NEC chip card use D720100A or D710101 chips.
Michael