  The low energy region of certain transition metal compounds reveals dramatic
correlation effects between electrons, which can be studied by photoelectron
spectroscopy. Theoretical investigations are often based on multi-orbital
impurity models, which reveal modified versions of the Kondo effect. We present
a systematic study of a multi-orbital Anderson-like model, based on a new
semi-analytical impurity solver which goes beyond simple modifications of the
well known NCA. We discuss one-particle excitation spectra and in particular
the role of level positions and Coulomb-matrix elements. It is shown that the
low-energy region as well as the overall features of spectra critically depend
on the model parameters and on the quality of the approximations used. Recent
photoelectron experiments and corresponding existing calculations are put into
perspective. An interesting crossover scenario between different regimes of
ground states with characteristically different local correlations is
uncovered.
