Unfortunately I was actually looking for the AKG's, and when I tried out the Q701's at an audio shop, I was mildly disappointed. Then the clerk said to try the HD600 and I honestly felt they blew them away... except in separation and soundstage. I then asked to try the SRH940's and was pretty impressed for a closed headphone, and for its price especially. And for the dt880/600, I tried a 2003 model, and liked them very much; not sure how they compare to 2005's+.
I didn't expect to like the sennheiser's, coming from senn IE8 iem's, I figured sennheiser had a darker sound sig; but the hd600 proved me wrong. I'm guessing the HD650 are darker, so that's why I ruled them out.
Originally Posted by NA Blur
Have you tried AKG K701's or Q701's? They are both really comfortable and strong competition for th HD-600.
The DT990 looks really bassy according to the frequency response, but honestly I find it really well balanced with the mids and highs. If you are looking for something bright the AKG's suggested above will be more your style.
I hope you find what you are looking for.