Thanks for posting that.
The question is does this justify $500 plus shipping to and from Minnesota?
I own the 3.7i and have never listened to the 3.7. I avoided hearing the 3.7 while it was out of my price range.

I don't know how you can answer that question, other than being able to hear the two models back to back for yourself. *I* would pay the premium to get the improvements the reviewer described and to the extent that he described them, but that's an opinion based on an opinion.
I've had enough experience with Mangnepan that I don't suspect them of being the type of company that would risk ruining their reputation and relationship with loyal customers by charging $500 for nothing/a speaker that doesn't actually sound better.
Looked at another way, $500 plus shipping doesn't seem like a lot to add to a $5k - $6k investment to a) get reportedly significantly better sound and b) not to have to wonder what you're missing. Again, that's my opinion, of course.