New Magnepan MMGi

no, but the move to x.7 was a big one and I've heard & compared the 1.7 and 3.7i

Maggie will tell you that an i is not considered a full numerical upgrade

a dealer should let you listen, and borrow maybe

Magnepan seldom divulges much information, if and when, they do any upgrades.  The (i) version was known to have a different tensioning of the mylar and maybe a cap or two in the crossover was changed.