Exactly what do you mean by “a small” call center. Where do you want to set it up? How much are you willing to invest? How soon would you want to expand it? What kind of work do you want to start of with?
Generally speaking, for small size call centers, an ASP is a perfect solution. Depending on the size initially 512kb to 1Mb bandwidth is sufficient. Celeron machines are okay. You do not need any high fi servers. A decent Pentium IV will do.
Give me more details or publish your email address so I can send you more information.