Each server has 4 NICs but only 2 in use (+2 spares). They're Sun X4100 M2s with dual quad core CPUs and 32GB RAM.
Each has a connection to the public internet via switch and a private non-routable interconnect at the back to each other, so all server-server communication (like transferring images, or database queries) doesn't happen over public channels.
I'd like to put in more servers, maybe a couple on the west coast, but it's all too expensive to do much in the way of expansion. These sites haven't only run at a loss, they've had $0 earnings for about 2 years. Even the other site which used to at least make half the hosting costs makes nothing at all these days.
Maybe I should look at refreshing the advertising over there.. ah well. One day