To me the AKG 701 and Q701 sound much more up front compared to the HD-650 which is a great thing. The one thing I really could not stand was the veil of the HD-650 and the HD-600. Just trust me and stay away from these. Even driven by an m903 they sounded veiled. It will drive you crazy some day and you will regret purchasing them.
As for the AH-D2000's I am not sure why people hear the "shrill" treble. Listen to some Great Big Sea through some AH-D2000's and you will not hear any shrill treble. Grado's on the other hand will have the shrill treble. I mean the only music I find shrill through my AH-D2000's is metal, but most metal is just too full for most headphones. Perhaps it is the amp that people use or the lack there of that makes the D2000 shrill. I drive mine with my m903 and have used the Ultra Desktop Amp with them as well and they sound great through those amps. I would not hesitate purchasing some AH-D2000's, but make sure you do it through a reputable dealer as there may be fakes out there.
All of Shure's headphones sound tinny to me. I like the neutral presence, but if you listen for the tinny nature of the Shure's you will begin to really hear it.
The AH-D2000's cover all other music awesomly, but they fall a bit behind for old classical. This does not mean they are horrible here. Unless you spend 70% of your time listening to only old classical perhaps the D2000's are not for you. When I listen to music I find myself going back to my D2000's 90% of the time because they sound so smooth. I am listening to John Williams right now with my D2000's and he sounds great. I think with classical you have to use an up front sounding can or you loose some of the immediacy of the music. Open cans do well with classical because they image better than a closed can.
Here is what I hear in the K701 Q701 vs the D2000
K701 and Q701
These are an up front sounding can, very open, and after 200 hours of burn in balanced sounding. They are extremely comfortable making them my can of choice for comfort. They extend well into the bass and better into the treble. They are a tad harsh right out of the box, but this mellows after a few days time. These are great for all types of music and sound a little more up than the D2000's which is slightly better for classical.
These are well constructed and nice sounding cans. They are slightly bass heavy. More so unamped which may be boomy for some. They have a nice crisp presentation from bass to treble. Amped they are truly amazing. They excel at rock, jazz, and classical guitar.
I would ask yourself if you would prefer a little more bass then get the D2000's otherwise the Q701's would be my recommendation. Both are excellent cans and I doubt you can make a bad decision choosing between those!
A fun track to listen to with the D2000's is:
Royal Crown Revue - [Ska The Third Wave - Volume 5 - SWING IT!! CD1 #01] The Walkin' Blues