Hifiman build is something you are willing to sign up for or not. Part of the pre-purchase decision tree for sure. I LOVED the HE-6SE, just could not live with the awful case, pads and cable for the price. Felt the same way about the Sundara. The HE-6se is probably the headphone sound I have liked the most, but I couldn't live with the QC tradeoff. Some certainly would. Coincidentally, my THX 887 has developed a scratchy pot. Just a reminder that a lot of the Chinese made units are a roll of the dice. They do offer great value proposition though. Personally, I lean more and more towards paying more for higher quality and better service. My perspective there has probably changed with life stage more than anything. That's where I would stand here. I wouldn't buy the 5XX based on the QC, just not worth it to me. I could certainly make the argument the other way though and find friends that I may suggest them too.