http://www.rme-audio.de/english/index.htm
they have a really good newsgroup too... very informative. I use a multiface with the pci card on my studio computer then with the cardbus card on laptop... great converters, low latency... and very stable... they know how to write their drivers...
if you go with a firewire based interface, be careful about compatibility... some firewire controllers have some major issues with audio interfaces.
peace