We report on circularly polarized Gaussian beam spin angular momenta that can be inverted upon scattering with quadrupole plasmon modes. The conditions for such conversion are met with high-angle collection, dark-field scattering microscopy on spherical plasmonic particles. We further report that silvered nanoporous silica microparticles exhibit a strong nonlinearity in their scattering, specifically a reverse saturated scattering (RSS), when exposed to high laser power densities on the sample of ca. 5 GW/cm