If you haven't already, check out the headphones section over at
www.head-fi.org and put your question to the guys over there. I'm sure there are people over here that know their stuff, but the fellas over at head-fi are nuts about headphones!
FWIW I have a pair of HD650's that I'm very happy with, although they are amped and I've upgraded the cable. Plus I'm a music man so I wouldn't be able to give a proper opinion on how they work for films. All I can say is I'm very pleased with my setup, but it didn't come cheap.
Hopefully someone else will chip in with some useful advice! Good luck