I can't attest to much in the way of a comparison between those you've listed, but I have owned the X1's for about 4 months now. The clarity of the HD650's, from what I've heard, is very good; but they will require decent amplification (300ohms). I can tell you from my experience with the Tesla T1's that high impedance will be a potential source of frustration and overall not letting them reach their potential. The E11 can provide slightly more power, but will not effectively drive the 650's. As purpleangel said, the X1's are much more efficient (30ohm). The AKG's are about half as efficient (62ohm), but still much lower in impedance than the 650's. You shouldn't have any issue powering those two.
Now as far as the X1's are concerned, I can attest to their comfort more than any other part of them (you mentioned being uncomfortable with the others). They feel like I'm not wearing anything and experienced little to no fatigue after hours of constant use. The sound on the X1's is noticeably less tight than the T1's (they better be for the price gap) and are less bright I would say, but that's not a fair testament to the X1's, as the T1's are known for their treble response to a fault (occasionally shrill and fatiguing). The treble is occasionally bright on the X1's, however, which surprised me. The bass response is full for sure, and the mids aren't extremely forward. I would describe their frequency response as being fairly V-shaped. Decent separation, but nothing spectacular. The redeeming quality in the X1's that I've found is their comfort, and that's why I still own them.
Overall, you won't be able to power the 650's effectively, but they may be more to your taste if you can provide them enough power.
Anyway, hope this helps. Good luck!
