A few people pm me about the differences between the SR-007MK1 and SR-009S. Here is my opinion between the two headphones.
SR-007MK1 is more laid-back presentation with better bass kind is like Sennheiser HD650, SR-009S like Sennheiser HD800 brighter presentation more forward. Instruments sounds better on the SR-009S probably due to its technical ability to extract details over the SR-007MK1. Dynamic wise probably the SR-009S edge out the SR-007MK1 but not by much. Both headphones are very competent, comes down to your personal preferences.
Most of the characteristics between them are quite similar, not a drastically improvement going from the SR-007MK1 to SR-009S. In the end, hearing the headphones yourself will probably the best of course not everyone do have the luxury to do so. Those are just my opinion once again, may not be the same for everyone else.
Dynamic: SR-009S 10, SR-007MK1 9
Speed: SR-009S 10, SR-007MK1 9.5
Tone/Vocal: My preference SR-007MK1 10, SR-009S 8.5-9 if you listen for long time, if short session it will be 9.5
Soundstage: SR-009S 10, SR-007MK1 8.5?
Imaging: SR-009S 10 for sure, SR-007MK1 9
Detail: SR-009S 10 detail monster, SR-007MK1 8.5-9
Bass: My preference SR-007MK1 9.5, SR-009S 8? Only out of T2 is 10
Midrange: Again preference SR-007MK1 10, SR-009S 9.5 for short listening, 8 for long listening.
This is out of T2 only, so scale rating is meaningless from different setup keep in mind.
I had the chance to test the 009s on the WES (good), t8000 (meh), and BHSE (excellent) and personally didn't like it as much as I my 007mk1. I agree with your assessment, the 007's mids are better, and the bass is (much) better. Overall, I found the 009s more resolving but unnaturally sounding; the timbre was just not as pleasant to my ears.
I'll add that I also had the privilege of testing the X9000 on the same above amps, plus the Eksonic T2 (wow!. Less of an evolutionary headphone, rather a distinctly new one. Somehwhat laid back across the entire FR, while exceedingly resolving at the same time, I found it made the music very holographic and a pleasure to listen to. I kept going back to them. One day...