SR-3N
Have tried to buy a pair of SR-3 or SR-5 on and off for over a year now, losing around 10 auctions. Really wasn't expecting to win this one either, oh well. I don't even listen to headphones anymore.
Probably same idea Fostex had with their oddly arranged hole patterns. There definitely isn't too much total hole area though.
Have you tried playing around with the stepup trafo settings vs frequency response?