Hearing that you had to return your XS's twice because of quality control resonates with me heavily. I went through 2 pairs as because in the left earcup at certain frequencies there was this resonating buzz. However, I love the XS's sound. So, I went back for a second pair. Returns were easy since the seller I bought from has a great return policy, and sadly the second had the same issue.
I got a pair of LCD-2C's for quality control and while they were built very nice, I honestly did not enjoy them (prolly listened like once or twice and now they're just sitting lol). So it was back again for a third XS and it those are the current ones I'm using today. Nothing I've tried has been able to match them for my liking and it's so frustrating because I'm willing to pay for something else that's built better and sounds the same or very close (with a wee bit more bass maybe but EQ covers me for that). Mainly what I think I tend to enjoy with them is the soundstage and imaging. They're so wide and open sounding that when I go from a closed back pair to them I really notice. They have like... I want to say 'height' to the soundstage but I dunno if that's the proper term to use. Probably due to the long planar driver. That and the texture of instruments really pops out as well. Kick drums I notice with the XS's really pop making a chunk of music I listen to fun. Female vocals can be super nice and no song I have makes them sharp sounding. I have lots of things to praise sound wise, but the build quality is just such garbage and I hate that.
I know when the ones I have die I'll be pretty upset because I'll be back to the lottery again with them. I really hope something else comes along to dethrone them for my liking because they really are my endgame. The Meze 109's did pop up on my radar too so this post was a good one for me to read.
Really? That's weird. Perhaps mine was different because it was there at certain high and low frequencies. Admittedly I was a bit afraid to go poking around and "fixing" the super expensive headphones I bought so I just opted for the return. I just hope nothing happens to pop up with them. Thankfully they're desk headphones or the most part so they're not getting knocked around or dropped or anything. Believe me when I say that I'll make a post on here if the current pair I have dies. I think I'm actually past the 1 year mark with them now!