work, Colafrancesco, Profumo and Ullio calculated in [@Colafrancesco:2005ji] the complete multi-frequency spectrum, for the case of the Coma cluster, resulting from dark matter annihilation. The emission spectrum extends from radio to gamma-ray frequencies, and includes the secondary emissions from the non-thermal electrons and positrons produced as final stable particles in dark matter annihilation events. In addition, Ref.  [@Colafrancesco:2005ji] also studied the heating of the ICM produced by the energy injected by dark matter annihilation, as well as the induced Sunyaev-Zeldovich signal. As far as indirect signals from particle dark matter annihilation, by far the best studied non-thermal radiative emission is the production of gamma-rays [@Gunn:1978gr; @Stecker:1978du]. Specifically, when two dark matter particles annihilate, gamma rays result both directly from loop-suppressed diagrams as well as from the subsequent decays or radiative emission (e.g. from final state radiation) of standard model particles produced in the annihilation final state, like quarks, leptons and gauge and Higgs bosons. The resulting gamma rays have energies extending up to the kinematic limit set by the WIMP mass (the pair annihilation event occurs for highly non-relativistic dark matter particles), predicted to be in the 10-1000 GeV range in the best motivated models [@dmreviews; @kkdm] (see however [@profumoheavy; 