I would go with the new Wilson Loke. This subwoofer recently received sterling reviews in both TAS and Stereophile. It goes very deep and its defining quality is its speed. With your speakers a super fast sub is a necessity. Though expensive, I believe Wilson subs are a cut above these other subs. You get what you pay for. You will not be disappointed with a pair of these subs running below your Magnepans.

Best

Charles