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Normally, you would only need one PQ and that's all that's provided by the 2960 and many other switches. The reason only one PQ is provided, it provides absolute priority over all other queues so it you had more than one, how would they have priority over each other?
On Cisco devices that support CBWFQ, you can have multiple priority classes but they all share the same LLQ (same idea as a switch's PQ).
Also on many Cisco routers, they support an older form of queuing, priority queuing. In this scheme there's 4 queues each having absolute priority over lower ranked queues; high > medium > normal > low. This could be what your client has in mind, but using this scheme it's very easy to ruin the performance of much of your data traffic.
What your client probably really requires is a switch with at least 4 queues (earlier switches either had just 1 or 2, some bigger switches offer 8). Of these, probably one should be PQ capable (normally used for real-time apps, e.g. VoIP).
4 queues, one PQ capable, are offen sufficient for many QoS needs. The non-PQ queues can be adjusted to a proportion of bandwidth.
