Hardware Requirements for Building a Gigabit Router

I watched both the pfSense and the inbox.exe tutorials, but still had a few questions. Do the hardware requirements change for routing a gigabit connection? Also, would the ALIX board be able to handle it? The computer that I'm looking at using runs off of a Pentium D processor, and 1GB of DDR2 memory. Any help would be very much appreciated. 

What speed is the pentium D? I have a phenom II x4 at 3ghz which handles it no problem, so I'd say anything around 2ghz would be okay. You'd definitely want to be using intel NICs though otherwise the CPU overhead may be too much. And maybe look at getting some more RAM, 1GB should be enough but 2 would be better.