I find the Opti 2 port ones work well.

you can get them all over ebay used.. doesn't matter if it says MAC COMPATIBLE or not.

like this: 6+ bucks, Free shipping etc...

http://www.ebay.com/itm/Diamond-Thesis-OPTI-PCI-DUAL-USB-PORT-ADAPTER-CARD-MP861-2-/291029765887?pt=LH_DefaultDomain_0&hash=item43c2b9ceff

Same as the one that is in my PM6400 right now.



More specifically:

I/C info:

OPTi

FireLink

82C861