Hi Brad,
As far as I know, Thom Palazzola still carries the Magnepan line in St. Louis. He moved his inventory out of his old place (Flip's Stereo) over to Alpha Tech Electronics where he has a room over there. If you call Alpha Tech at 314-645-5250, Zaw can get you in touch with Thom.
As far as mine go, I have the MG-12's and I found the crossover mods to be very easy to install and they do make a big difference in the sound. The 1.6 mod parts are larger and probably will require mounting the components in boxes that sit behind the speakers. Again, they are fairly simple to install. There are several threads on crossover mods on the AudioAsylum/Planar/ Articles and Tweaks sites.
Warning! Once you're hooked by the maggie sound, there's no going back!
steve