We have undertaken a series of studies of Magellanic Cloud (MC) supernova remnants (SNRs), utilizing the high spatial and spectral resolution and sensitivity of instruments aboard Chandra and XMM-Newton, as well as supplemental observations at optical and radio wave-lengths. Here we present the findings of some of our recent work using these X-ray observatories. Our study has focused on older, well-evolved remnants, allowing us to examine the later stages of SNR evolution. The sensitivity and depth of our observations have enabled us to detect previously unseen X-ray emission from large, faint shells. In addition, the superior spatial resolution of these instruments has allowed us to distinguish particular X-ray features, including two new candidates for pulsar-wind nebulae (PWNe), and to perform spatially resolved spectroscopy for these SNRs. Using these data, we study several SNRs in which X-rays generated at the shock front no longer dominate the emission, leading to a central brightening in X-rays typical of "mixed morphology" SNRs. Further, we investigate regions where two or more SNRs exist in close proximity, with the possibility of multi-SNR interactions. In each case, we analyze the physical properties and progenitor types of the SNRs.