I've purchased mine for around 150$. I am not an audiophile, and I do not have an amp. I've had these for almost a year.
The headphones are entirely made of plastic, with no hinges whatsoever. The cups tilt a bit up and down + left and right. The headphones are built very well in my opinion. The headphone itself is "Open-back", meaning people around you can hear what you're listening to, and you can hear people around you. The original cable did not last me very long, and it can barely connect securely to other devices. You will definitely have to swap the cable on these.
The velour pads are very comfortable, and while the head cushion is a little bit thicker and harder than you might expect, these are easily the most comfortable pair of headphones I wore.
For 150$, these sound amazing. The sound is very clear, and it does have the sennheiser sound signature. Compared to the HD559, the HD579's are clearer than them. The mids shine here, and the bass is enough for me. Sennheiser Headphones are known to be "lacking in bass", although I enjoy the amount of bass they provide, even if they are clearly not meant for bassheads. The highs are also great, and vocals sound very clear on these headphones. I've listened to the ATH-M50Xs, and the sound signature is much warmer on the HD579. The clarity on both headphones is amazing, and for me they are very close in clarity and sound quality. I've also listened to the HD6XXs (without an amp, mind you) and overall I've found the HD579 a bit more comfortable, while the HD6XX's sound is a bit more detailed (The HD6XX's do leak more noise than the HD579's). Overall, if you have the money or you already got an amp, the HD6XX will definitely perform better, but if you're like me, these are a great "entry level" pair of headphones.
At just 100$ on this drop, these are more than worth it, but if you already own a HD5x8/HD5x9 series headphones, these are not a huge upgrade. The sound quality on these is absolutely great, especially when it's considered an entry level headphone pair. For the price, I don't think there is a better headphone pair on this site (not even the HE-350s).
-Build quality is solid
-The cable is not very good, so I would suggest you to replace it
-Price is as low as it can go right now, but the US and Canada shipping can limit some people from buying it or consider it.
-Headphones are open backed
-It has the same earpads and 2.5mm locking mechanism that other HD5XX series headphones have
-The foam removal mod can work on these headphones, although I didn't try it myself.