Speed kills....

Duke,
You work in an interesting way and present what you do quite convincingly. I wish you success.

I don't know why Duke introduced Stax headphones; but that was exactly what I thought when I read the OP.  Is there any way you could audition them, Russ? 

???
2channel8: I have the Lambda headphones with an SRM-1 (mark2, I believe) amplifier.  I'm trying to replicate that sound but on a larger scale.  

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.