We present a novel implementation of selected CI (ICE) including non-abelian SU(2) symmetry with an emphasis on efficiency. A detailed comparison of the SU(2) adapted selected CI with the usual determinant based CI and DMRG is performed in order to access the efficiency and accuracy of the ICE method. Finally, we present a few case studies which demonstrate the power of the SU(2) adaptation as opposed to the determinant representation. Our method seems especially effective for describing the wavefunction of molecules containing a number of transition metal atoms interacting via a strong anti-ferromagnetic coupling.