Graphics cards in a Server are irrelevant, that's why you find things like ATI RN50 graphics in Dells poweredge range.
Network cards may or may not be important depending on what you're using the network for, if you're sharing media to a single machine then the onboard will more than likely hack it, although the more budget orientated network connections use lower quality ASICs which can reflect in your transfer speeds. If you're intending to get into the whole server/client (Domain) orientated system and implementing any of the technologies which go with it then you want to give your server as much network bandwidth as possible, partly due to the constant discovery/authentication/timing interaction that goes on between server/clients and partly for speed profile transfer/shared file access.
You can get dual/quad port network adapters reasonably priced on the e of the bay, and team them into a single fat pipe but you'll need a reasonable quality business class switch to gain any benefit from it.
