I don't own the SRH940 and only listened to it a few times, but I'm quite surprised that you find it more detailed than the HD650. It didn't own the latter at the time, but I compared it briefly against the DT 1350 - and I found the latter more detailed (gear used : iPhone 4 + LOD + TTVJ Slim). And as I find my HD650 as detailed or maybe a little more than the DT 1350 up top out of the same setup, that seems strange to me.
But that may be related to the HD650 rendition of details and electronic music. I find the HD650 to have a very subtle rendition of details : they're not thrown in your face à la DT 1350 (with the latter, every bip and pop of a recording can't be missed, while they're more integrated within the rest of the music on the HD650 - but still there if not more detailed). For the genre, I actually like the DT 1350 laser-cut rendition of details - it gives drive and tension to the music. But every time I listen to classical music, I find the HD650 treble rendition better - timber is better, it's much better integrated within the rest of the music, and it remains as detailed if not actually more.
Maybe the amp isn't good enough also.