The closest I've gotten to a SR009 that isn't a SR009 is a HE6 with top-quality preamp+amping in terms of resolution. Tonality is a little darker on the HE6, 009 is definitely brighter, and both HE6 and 009 have etch to my ears.

The 507 doesn't sound like the 009.

I'd assume what Zowki wants to do is stick with electrostatic headphones so he can get a good amplifier ahead of the 009, correct? I've only heard the 009 twice, once on a DIY KGSSHV and in another room at a meet with a Eddie Current Electra, and none of my friends nor I really liked the 009 with the KGSSHV. May have been the giant OPPO DAC/BD player screwing things up, I don't know. I can only speak from my experience, but my favorite stax lambda I've heard (out of the SR-lambda SB, Lambda nova, lambda nova signature, SR-202, SR-207, SR-404 and Airbow SR-507) would be my personal setup, the SR-202 with SR-507 pads. It lacks the absolute transparency and detail retrieval of the 009, but it doesn't sound harsh like all the other lambdas I've heard. Of course that's just my own shitty opinion though, so take it with a grain of salt.

Vegan pads remove the treble harshness on HE-6 IMO anetode, they even give me a similar impression that the 009 did in my very brief sampling of it if I EQ out some 200hz.. Not that I would pick them over the other mentioned headphones when looking for the 009 sound

The vegan pads could perhaps mitigate that troublesome harshness, but they could never quench my irrational hatred of the HE6.

Thanks for all the advice so far. I don't mind getting a non-electrostatic headphone so now I'm deciding between the Stax SR-202 and Hifiman HE6. I used to own a Paradox and really liked it but I would prefer an open headphone for the soundstage.