Here's the dmesg for my Tor exit relay, which runs on a D2700. It moves about 2.0-4.5 MB/s in each direction.
Hmmm.... that's nowhere near as fast as what we do, and not even as fast as a P3.
It seems to be running at full capacity doing so,
I don't know much about tor. When you say "full capacity", do you mean the hardware was maxed out, or that you were doing the most that the tor network would allow you?