Weatern Digital makes some of the best hard drives and they have ones that are specicly for raid arrays and others that are good for eberyday use. Mostlikely you want a 64 mb cache drive. It will depend on what size your looking for, 2 tb or 3 tb.
HP and Dell make good servers, what is your budget?
Do you have a router already for internet? If so that may influence your choice of "hubs". I recommend gigabit switches between your workstations and router. There are lots of choices but Cisco is great.
The choice of ram does not have compatability issues just as long as it's DDR3.
The hard drives I linked before come with software that is a must have for a file srver setup and will add to the security and operation of the server. The cpu should be a Xeon cpu and the model will depend on the budget. For internet connectivity in a server I would go with;