VMan:
Bert will probably laugh when he reads this, but I have decided that I am pretty satisfied with this cheapo Visionman server from TigerDirect.com. It's going for $549 with your choice of OS.
http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=2606265&CatId=3370I am running 6 PC's (wired), a laptop and two tablets (wirelessly) off this thing. I am not even using all the capabilities of this very low-end server, and my network is plenty speedy.
I am using the MonitorMan as the storage place for the AC database, but I am not really running any server OS. I am just running Windows XP Pro, with a generic router for the wired PCs and the best LinkSys wireless router you can buy at WalMart.

The guy that initially set up my network was either a crook or a moron (or both, more likely). I had to undo what he did, and stick my system back together in a very simple-minded way that I could understand (I am a networking numbskull).
Bert is right that you should stick your server in the corner and just let it serve files. However, I have been known to fire up Dragon NaturallySpeaking and Amazing Charts simultaneously on the server without noting any loss of speed on my network.