Due to circumstances I cannot address now and for the near to mid future, room treatment and good monitors are not really feasible for me. I would like to heighten my mixing skills though and have shifted towards looking at open back headphones. I do have means such as receivers/stereos, vehicles, and other speakers to real world check mixes on. Currently, I own a pair of Beyerdynamic DT770 Pros so my initial inclination is to pick up some 990s and call it done. However, I have two questions. 1. Do any of you think the other open back cans in the same price range ($150-$250) offer improvements or better options over the 990s? 2. Do cans like the Sennheiser HD650s and AKG 701s have enough, if any, of a performance increase to justify their cost over the 990s in your opinion?