Yes, I think the K701 is a lot like the HD800...it seems to have very specific amping requirements to match my tastes.
IMO, this "plasticky" midrange as I hear it, is an upper mid peak (upper ranges of females vocals and where a lot of transient information takes place) - a strength because of the details but for my ears, also a flaw. Even when paired to a warm and bassy amplifier, this flaw still occurs, but less aggravating.
The total solution for me was not a "warm" amp, but a "midrangey" amp...in that an amp with a specific peak in the central midrange eradicated the upper mid peak (a peak is only a peak comparatively, if we boost the neighbouring frequency that the peak is peaking from, we no longer have a peak).
Lean tube amps is what the doctor ordered for me. Incidently, when I hear that Jason Stoddard believed that the inexpensive Schiit Valhalla synergised the best with K701, and then reading that the Valhalla was not warm, but rather lean, I was not at all surprised.
The K701 and the Ming Da amp (not warm but very midrangey and a little dark) did the trick for me. I also switched it to the solid state Lehmann Black Cubed amp...and the K701 sounded a trace warmer with the Black Cube amp...but that upper mid peak was very noticeable, and the added warmth did not actually help in this case at all. The Black cube was not a warm amp, but also a little lean overall.
I don't have either amp anymore, but these days, I run the K701 balanced with the Phoenix and Reference 7, outright, the Ming Da was still slightly better (I picked mine up for just over 300 bucks brand new from ebay). The Ming Da was something special, it didn't matter what source I had it connected to, it was so colored in its own distortions, that any source differences are just about overuled by the tube euphonics. Source was a non issue with the Ming Da amp, very unique in my travels, I pod worked just fine. But whatever strong flavour the MD had it just matched the K701.
I use my K701s exclusively at low volume listening, where it gets a majority of my head time, only the LCD2s can claim more overall head time from the K701s. This time around, it is used exclusively with a free crossfeed plug-in called headfit, which absolutely solves the midrange glare, whilst at the same time warms up the sound - the MD amp couldn't do this, nor can my warm amps. Imaging and instrument separation becomes very exact with this crossfeed.
One does not need to spend a lot to amplify the K701 correctly and satisfactorily. My belief system also goes that the midrange glare I heard may well be non present to someone else which happens to have a HRTF that corresponds well with these nice cans (but compared to other cans its always there regardless - or other cans are too surpressed at the upper mids). The K701 makes some of the best trebles to my ears....comparatively rolled off after about 12 khz.
My HD650s were superseded by the LCD2s, but I have yet to supersede the K701s...the HD800 could have been....but I found it too bright in the treble - the HD800 scarred me from its signature after using it exclusively for many many weeks. Often I just wanna hear all the details in the music and enjoy music from a different distance. I still can't see how anyone could only use one headphone. The HD650 with a bright recording sounds the same to me as the K701 on a warm recording.
