OK, I finally set this up and my results are worse than expected. See the attached SiSoft Sandra network benchmark...

I am using Cat. 5e cable. Should I be using Cat. 6? Could that be a problem? Cat. 5 doesn't work at all.

EDIT: Actually, looking back on it, these results are quite good. I was looking at the Firewire score thinking it was 100Mbit ethernet without paying attention to the numbers. I am sending flacs over the network now and it's taking about 1 second per song.