Sennheiser HD 600 [amazon.com]
are having their 20% off for Prime members with either the Amazon Rewards Visa or Store Card that lasts until the 22nd. The e-mail I got only shows a picture of the Visa but the link to the site shows both.
The wording is confusing but it looks like the store card will work too but they're probably just trying to push people to sign up for the Visa instead because it lists the store card at the bottom.
They also have the Sennheiser HD 650's [amazon.com]
for $245 after the 20% off.
It's been the biggest debate in the history of headphones on which one is better. Both are amazing but more lean toward the 600's being solid in almost every area where the 650 is a legit 100% pure critical listening that people in studios use with it being more flat than the 600's so it would be better for Jazz or classical music for example.
I think there is some bias also because back in the day most couldn't afford the 650's which were their flagship but now both are close and coming down in price with the new model coming out soon. Zeos [youtube.com]
, one of the most famous reviewers breaks it down between these along with the HD 700.