Suggestions for inexpensive PCI Express USB card?

[MixerGuy]

EricM of Digidesign recently said on the DUC:

“We've found that, in the cases where we've been able to reproduce this (Mac Pro Mb-ox1 random loud noise) problem, it can be solved by installing a PCI (Express) USB adapter, and plugging the Mbox / Mbox 2 into the PCI (Express) USB adapter rather than using the built-in USB ports. PCI (Express) USB adapters can be had for less than $20 these days. If you'd like to try this out, we'd love to hear whether it solves the problem on your config. However, please be aware that we can give absolutely no guarantees that this will be a solution.

So - any tips for a cheap PCI Express USB card for my Mac Pro? I’d love to buy it on the internet and have it delivered to me. Bonus points if it has FireWire 400 on the PCI EXpress card as well, but is still inexpensive....

many thanks