I don't think you'll find such an animal. At a guess, I'd think that due to the expense the most likely speakers to use rare earth magnets would be hifi, not guitar, although I haven't looked into guitar-related things in a while. The last cabinet I bought was either the Hartke or the SWR, either way, it was several years back and things may have changed. Unfortunately, there aren't enough hours in a day for me to keep up with everything, all the time.
Grey