So this is interesting. I saw that Drop.com just released a new HIFIMAN headphone,
the HE-X4. What's interesting about it, is that it appears to have the exact same driver as the HE400se International Version (no "Stealth Magnets") and according to a review that did a direct listening comparison and measurements of the Stealth 400se and the X4, those rounded magnets don't make any audible (or measurable) difference in this design, at least. The real kicker (to me, at least) is that the X4 is ~$20 cheaper than the current going price for the 400se here in the USA. Sure, you can get a 400se for $100 on Taobao, but unless you live in China, by the time you pay the freight forwarding cost it's almost certainly going to be north of the X4's price.
I was tempted with the 400se but I'm now even more tempted to pick up an X4 and just mod the heck out of it and see if there is any room for improvement.