You would probably get more money selling individual components rather than a whole PC.
Most people these days (typical home users - no self builders) would go down the Dell type route and have no idea what half the stuff in your PC is. Its a shame because although your hardware is not the latest, its still a decent set up.
+1 for parting it out. You'll get more that way, but you might end up being stuck with some random things. It never hurts to list it as whole anyway, sometimes they do go for what they're worth. The problem is, you have some parts there that the average consumer won't know the value of.