Well I got my Sundaras today.
No defects I can see and working perfectly. The metal construction is nice, solid. More substantial than the 400i, although I actually like the plastic aesthetics of the 400i slightly more (the more "basic" metal look of the Sundaras is also nice looking).
I will say that the band size adjuster is very hard to slide, to the point that I was worried about breaking the plastic sleeve. But that's not much of an issue as once it is at the right position for one's head, it need not be adjusted again. (Unless you will share this with someone; then it could be a real issue).
I also find the pads somewhat uncomfortable, but most pads have to "mold" to my ears before they really feel comfortable. This can take weeks.
As for the sound quality, simply put, I'm impressed. Very. The Sundaras are not a slight or negligible improvement over the 400i's imo, but a significant one, perhaps a dramatic one.
A/Bing the two the difference is not subtle; nor is listening to well known tracks through the Sundaras. I won't get into exhaustive comparisons (plenty of others have done that), especially since I've only been listening for a few hours. I'll just say that they do everything the 400i's do, but better. This is apparent on both the large and smaller (more subtle) scale. (And the subtle improvements, which often take time to notice or appreciate, are often what really count in a vast many things in life imo). Particularly impressed with the smoothness and cohesion of the sound, the clearing up of the mids (much less congestion and more instrument separation), and more bass impact and slam (something that not being a basshead I didn't even think I missed). And they have that good PRaT which the 400i's could lack; no problem handling fast paced rock/speed metal.
Probably the best thing I can say for the Sundaras is that I'm having a hard time tearing myself away from listening to them, and I keep queuing up favorite tracks (and well produced "test" tracks) to hear through them. I haven't gotten deep into all the genres I want to listen to yet (no classical, soul, folk, ambient, etc.) but the pop, rock, metal and jazz I've thrown at them they have all performed well and I've been very impressed (yes, even to the point of shivers) with their "take" on quite a few tracks/albums.
Really glad I finally upgraded, especially at this price.
Important note: I don't think the impressions above are just the "honeymoon/new toy" phase as with me usually my first impressions with audio gear don't change, I either like it right away (like, literally within seconds) or I don't and that doesn't change much if at all (and I'm actually tired today so it should be harder to get enthused over new gear and music, especially "energetic" music). And the Sundaras are still not perfect of course (there's a few things I think I'm picking up in the sound that aren't quite what I'd like), but they are 1) a big improvement over the 400i's and 2) quite impressive at this price point. And that's all I asked.
