Interesting. Slightly boosting the classic 840 mids. They have been my go to pair of phones for many years now. Especially for metal \m/. I have not heard the 940's but they are known for their detail in the upper frequencies.
Can only speak for the SRH440. Damn fine bang for buck headphone. Neutral and is good with anything: music or source. Soundstage is meh but in terms of musicality they pull their weight. I use mine at work with a Fiio E17. Oh and springing for the SRH840 ear pads is a must. Both for comfort and sound.