Virtual processor VProc is a combination of AMPs and PEs. you can have 128 VProcs per node but i guess that it need not be 128 AMPs and 128 PEs. May be combination of both can be upto 128. You may not require same number of PEs as of number of AMPs.
I may not answer precise to your question, but i can give you a point
we can have 1200 session per gateway. also we can have 120 session for a PE which means at max for a node there can be 10 PEs. This conditions stands good if it is a network attached system.
so i feel that we can have combination of AMPs and PEs to be max of 128 per each node.