If the machine is going to be dedicated (linux); hen it's the cheapest way just to use the standard mobo controllers and cheap-ass expansion cards. My 2.66 ghz p4 machine handles it just fine. I can always upgrade and alter the main hardware as long as I have MDADM running, I'm good. Or any...
I've recently moved my wrt54g v2 over to tomato from dd-wrt. It seems to be a pretty good amount faster IMHO. I am still tweaking the QoS but the Qos on DD-wrt brought it it's knees.
I run a network for 6 individual machines, a media center (very little traffic), a file server (most traffic...