Massdrop has partnered with Sennheiser to release the HD 6XX, based on the HD 650. I have a pair of the 650s and they sound amazing. The 6XX is supposed to sound identical but will likely have lower build quality to keep the price down. Theyre selling for $199 which will be closer to $350 with exchange and shipping. That's still a killer deal. Massdrop shipping can take forever (don't expect them for Christmas) but these will be worth the wait. Sign up now, I'm positive they'll sell out quickly.
https://www.massdrop.com/buy/massdrop-sennheiser-hd6xx