I would make sure that he stocks MA in the first place. Then you should ask for a pair of Magnum M3, Shotgun MA and Magnum MA speaker cables and interconnects for loan to your system so you can make the informed call.
Sorry, haven't had a chance to go through the regular Magnum line to compare, but according to MIT's own literature the only significant difference is "their ability to articulate effectively at lower and lower frequencies as you step up in the product line." Take that fwiw.
You must have a verified phone number and physical address in order to post in the Audiogon Forums. Please return to Audiogon.com and complete this step. If you have any questions please contact Support.