When talking open backs I think of AKG. I find they offer lots for the money. In your ball park the K702 for around $210 on Amazon.
There is also the K701 for around $220 and the Quincy Jones version Q701 for $240.
Grado's also sound great. The SR225e is $200.
AKG's are more available in stores while the Grado's are a boutique headphone. They are available direct form Grado with free shipping in the US for $200. Grado's are pretty much the standard and always well reviewed and many drool over Grado's jsut because they are Grado's.
After reading some reviews here is the lowdown. The Grado's sound great with a bit more bass. But the AKG has tighter bass, more overall clarity, and are much better balanced for a full range sound. When doing an AB comparison of both the k701 and SR225e, more of the music can be distinguished with the AKGs because of their clarity and full range balance. At first the AKGs may sound thin due to their clarity, but when ABing them next to others including the Gado's you hear the benefit of the full range sound.
The AKGs also have the single sided removable mini XLR cable that can be changed. The Grado's have a standard soldered 2 sided cable which is a shame. I love my AKGs and love the cables. The cable alone wins me over, but knowing their sound quality is very good is enough to warrant them a good look.
I own a high end pair of AKGs and love them. Many people find they prefer Grado, Shure or other headphones because they pump out lots of bass. Kind of how people think a $150 surround sound computer speaker system sounds amazing because of the big subwoofer. It's actually garbage sound and people just don't know any better. Or how young people put amplifiers in their car with a big subwoofer and it hurts to listen to their stupid hip hop music because of all that rattling sheet metal, and the shrilling tweeters that pierce your ear drums. They think loud = good sound.
I feel the same way about AKG. Their headphones tend to be more clear and of a reference design like studio monitors designed to not add any color to the original sound. I can listen to them for hours on end without hurting or tiring my ears. Some people do not like this feature and that's fine. They are worth a look at though.