I have the HD650 and Nuforce ICON-HDP amp and I love it.
The Stax SR507 drew my eyes before. Definitely stays in my mind. This might be my entry level to the Stax. If I pair it with old receiver, can it work to some satisfactory level? Now I can afford the SR507 but not dedicated Amp.
I am very happy that you asked this question. I also have been searching for this same type of headphones. I am a novice on this forum but after reading so many reviews it seems that the ones many folks like for classical music is the HD-600/650, ATH-AD900 and the SRH-1840. I live only 3 hours from Denver and will be going to the annual audio show there next weekend to listen to many headphones. I will update this forum on what I find out. I right now have the Denon AH-A100 which I really enjoy. I also own a few of the Grado phones in their stable and they are great for classical, especially the 325. But they kill my ears after a 30 minutes or so of wearing them.
I am most interested in the Alpha Dogs right now since they are closed back and I use the headphones 8 to 9 hours a day in a work environment.
K701 - stellar headphone, has a great reputation here, and recently discontinued. Bass and treble aren't as loud as the midrange, which puts off some people. It needs a little dynamat to avoid sounding a little plasticky. K702 - most people want more bass out of K701 and K702 sounds a little more balanced at that, plus K701 is now discontinued. There's also the often recommended Q701 lately, but I think that it sounds like @ss without removing the foam discs behind the little black grills.
Another vote for HD650 here, especially with chamber music.
Another vote for HD600, haven't tried it in a long time, but when I had it I listened to symphonies and/or piano the most with it. Great tonal balance. HD6x0 tend to sound more "believable" when it comes to vocals, strings, and more. K601 - A slight downgrade from K702 and such, subbass is AWOL. There's the newer version, K612, but I haven't tried it. Best tonal balance from AKG. HD558 - HD6x0 on a budget, lol! ATH-M50x with HD280 earpads or memory foam HM5 earpads - it sounds addictingly "right" and natural. With the original earpads it does not sound good with classical. HDH50 - best tonal balance out of everything mentioned here and probably anything else that may be mentioned later in this thread, although I don't know jack about the Stax listed or K340. Good for all types of classical, but better suited to small ensembles. K545 with HD280 earpads or memory foam HM5 earpads K501 - a downgraded version of K701 with the bass and treble dialed down further, basically. Subbass is also AWOL. Discontinued long ago and has a better headband. SRH840 - tends to sound more "believable" like the Senns mentioned, but is warmer in sound. It can be a bit harsh in the treble with some recordings.
1. W5000 - Not as neutral as the T1, and not universally popular, but I enjoy listening to orchestral, chamber (strings/piano/oboe) and vocal far more on this headphone. High detail and separation of instruments (on par with the T1 imo) and decent soundstage (smaller than T1, but larger than HD650 I find). Better timbre of acoustic instruments over the T1, mainly due to the more forward sound signature. You feel more closely placed to the instruments. Can be fatiguing as a result. Airier signature (which again will be fatiguing for some) than the T1, but equally as smooth.
2. beyer T1 - Largest soundstage, warmer than the W5000 and W1000X. Does exceedingly well with any classical music genre. Neutral and very detailed, with great separation of instruments. Sounds more balanced than the W5000/W1000X, and therefore less fatiguing, but less exciting/romantic sound.
3. W1000X/HD650 - I find the W1000X more suited to classical music than the HD650, mainly due to the better detail and soundstage. Slightly more distant soundstage than the W5000. Acoustic instruments (strings especially) sound more exciting than the HD650 due to its detail and brighter signature. Punchy bass. HD650 has a smaller soundstage, and less '3D feeling' in the sound. I feel the detail is there, but is more subdued. But it's perfect for relaxing and enjoying the music late at night, especially string quartets.
*Using W1000X with W5000 pads. Better seal and comfort. Slightly better bass impact compared to stock pads.