  The recent discovery that the Fe-K line luminosities and energy centroids
observed in nearby SNRs are a strong discriminant of both progenitor type and
circumstellar environment has implications for our understanding of supernova
progenitor evolution. Using models for the chemical composition of
core-collapse supernova ejecta, we model the dynamics and thermal X-ray
emission from shocked ejecta and circumstellar material, modeled as an $r^{-2}$
wind, to ages of 3000 years. We compare the X-ray spectra expected from these
models to observations made with the Suzaku satellite. We also model the
dynamics and X-ray emission from Type Ia progenitor models. We find a clear
distinction in Fe-K line energy centroid between core-collapse and Type Ia
models. The core-collapse supernova models predict higher Fe-K line centroid
energies than the Type Ia models, in agreement with observations. We argue that
the higher line centroids are a consequence of the increased densities found in
the circumstellar environment created by the expansion of the slow-moving wind
from the massive progenitors.
