audio interface for audacity on MAC OS X 10.5.8

I am working with Audacity 1.3.5.c on Mac OS X 10.5.8 (Macbook) and looking for an 8 Track Audio Interface with minimum 8 Outputs and 8 Inputs. It should work on USB 2.0, or better, on firewire. The interface shall be used for artistic sound installations. I have read a lot about compatibility problems in various forums. Does anybody have an advice which hardware is the best choice? And maybe there is something for sale?

You should not multiple post. I locked this topic.