I think the most important thing in determining the requirements is understanding what type of business you will be servicing. A key point to remember is that it takes people, process and technology to make up a good call centre. Technology by itself is of little or no use.
Generally, you will find that a small centre is constrained by cost ie what funds it has available to spend on a solution. If you are looking into CTI, could I suggest that you look at the many major solution providers. From there you will generally get ideas of what current industry trends are. Organisations such as CISCO, Genesys, Nortel, to name a few, are worth looking at.
Alternatively, there are some good online magazines which provide information of use. Generally, an easy way to find these is to go through a site such as the Call Centre Manager’s Forum and go to the links page.