The basic requirement to setup up a call center would be as follows:
2) Networked Client PC’s with server
4) Suitable infrastructure
5) VOIP gateway (with no. of ports same as that of agents)
6) Voice and Data network.
7) Headsets with Dialpad or phones as per your requirement.
8) Dialer S/w, CRM, Voice Logger, ACD
these are some of the basic things you need to setup a call center whether inbound or outbound, depending upon number of seats the pricing may vary for all the products, let me know if you need any specific information.