Our primary goal is to identify all phosphorylation sites that significantly differ (up or down regulated) between the treated and control group. I would also subsequently like to do some pathway mapping.
Have you read this paper, "Perseus A Bioinformatics Platform for Integrative Analysis of Proteomics Data in Cancer Research" by Stefka Tyanova and Juergen Cox? It is a good guide for analysing proteomic data & should help you if you are analysing your data using MaxQuant software.