Hello everyone,
 
Before anyone suggests that mixing on headphones isn't the right way to go, I already have Yamaha HS-5 monitors and they've done their job beautifully for my film score work and my Progressive Rock work as well.
 
I've been using a cheap pair of AKG240s that I bought a while back when mixing on headphones, and although they've done their job so far, I'm upgrading a lot of my studio gear and decided it's time to invest in better headphones as well.
 
I usually alternate between mixing on my monitors and headphones and also use my headphones a lot late night when I'm working. So far, for my budget, I've narrowed it down to between AKG702 or Q701 (Quincy Jones edition) and the Sennheiser HD650.
 
Please note this will be mostly for mixing my film scores, as well as my progressive rock project, but mostly for my scores, so basically a lot of orchestras. Which of these have a more neutral and flat response, with clear / defined mids and highs, without lacking or having too much bass?
 
Would appreciate any other recommendations you could vouch for. But I've also read a lot of contradicting reviews about the ones I mentioned, so if you could also compare them from personal experience if you've had them or tried them, I would highly appreciate it!
 
Thanks!
Mathew

In my opinion, the AKG702 reproduce a lot of detail and have a good sound stage but completely lack in the low end. The HD650 has a bit of a boost in the low end and have a slightly narrower sound stage with a little less detail.

I would say the HD650 or the HD600. I haven't heard the HD600'S yet but I've read many comments suggesting they are more neutral.

I agree that you should add the HD600 to your list of possibilities. It is quite neutral, a benefit in the work you do.  And there are also the planar magnetics HE400i and HE400S to consider. Any of those three could potentially work--in addition to those you've already mentioned.