Speed kills....

When trying to replicate Stax headphone SQ on speakers, don't forget to pay attention to the amp and power circuits. I liked Duke's linking of perceived speed to upper frequency behavior.  I've found improved transient attack to be the biggest benefit to having larger amps and better power cords/conditioners/multiple dedicated circuits. Add to that some treble clarity, and you also get air which is a trait I highly covet. I don't think I've heard horns match hard domes in that area, and definitely not electrostats. Larger speaker cabinets also move less and provide a better launch for the wavefront. YMMV and good luck!

@russellrcncom ,

Best of luck! I can relate. Let me know how you make out. in line with @nagel's comments, I've found a fast Class D amp leans in that direction. Mine's a Primare I32. I bet the I35 is nuts.

I love the title of the OP's thread: Speed Kills....
It takes me back to the old days of cars and drag races into the wee hours of the morning. Back then I wanted a t-shirt that read:
Speed Kills-Try It. 
I see it's very appropriate here as well.

All the best,
Nonoise

@russellrcncom, I too have the Stax Lambda (Pro) phones and SRM-1. Have you heard the Sanders ESL's? I heard them at the show in SoCal a few years ago, and found them very much to my liking, more than the current Quads.

Never heard them, but you may want to try:

http://www.eminent-tech.com/LFT8.html

Also, you may want to try other "planar" type such as Martin-Logan, Magneplanar, etc.

This may be your cup of tea.

Of course, YMMV.

Good Luck!