VIA cards are a problem because they use UHCI and not OHCI, or something like that. However I think starting with Tiger, UHCI is supported.

VIA is the only on who makes crap UHCI cards, so just avoid that chip and you'll be OK.

If a card is OHCI/EHCI (the USB 2.0 portion is EHCI) it will work in OS 9 but it won't work at the USB 2 speeds. Everything will work as OHCI and therefore 1.1 speeds.