The cans from my own experience with the best sound stage would be the K701/702. However, the barely have any bass.
If you want open cans with some decent bass, I would go with the Beyerdynamic DT990.
Sennheiser is right above the Beyerdynamic, at least for me. The HD650 is definitely worth the buck. They like the K701/702 have a crazy nice sound stage. They perform better in the bass department as opposed to the K701/702, but have less bass compared to the DT990. Moreover, I actually like the way they sound over the K701/702 seeing that to me, they sound a lot smoother, warmer, and don't fatigue your ears within minutes. I would also pick them over the DT990 because they are just perfectly balanced to my ears. The DT990 is somewhat colorful, I don't like the sound they produce that much.
- If you want to go with a huge sound stage and balance of everything else, HD650 is your boy.
- If you want amazing bass, look at the Denon AH-D2000 (closed-back headphones always produce great bass).
- If you want bass with a good sound stage, though not the greatest of all sound stages, look at the Beyerdynamic DT990.
- If you want just sound stage and nothing else, barely any bass, look at the K701/702 from AKG.
My pick for your preference goes to the HD650.