Warm and lush
is neutral, IMO. When was the last time a live show stabbed your ears with as much treble as most headphones put out?
The Harman curve is just one of several, other common ones headphones aim for are free field and diffuse field. Each one aims for different things. You can read up on the process
here. The Harman curve isn't present because it's fairly new, and designed to try to simulate the effects of neutral speakers at a distance in a neutral room. So some major factors include having a generally downward slope from bass to treble (because bass travels through air more easily that treble) with a peak at 3 kHz to simulate the effect our outer ear has on the vocal range. So, generally, warm and lush.
According to Harman the SR-009 is tilted upward slightly much like the HD800, but less up and down because of its more linear response, no midbass hump and smaller treble plateau. So if I were trying to match this curve I'd probably just apply a straight line going from 0 dB at 20 Hz to -5 dB at 20 kHz. That's pretty close.
Ultimately "neutral" in headphones doesn't really exist yet, there's too many variables and disagreements. It's a lot easier with speakers because they aren't attached to our head. They don't just simulate
what we hear, they simulate
how we hear it. Headphones are still working on that how. So in the end pick what you like, fix it if you need to, don't worry too much about neutral.