HEY!!!
Bob I have heard the STF3 and the EP350, I think the STF-3 (non-tunable version of the VTF3) maybe dug a little deeper and played louder, I do remember thinking it was beast when I had it in my room and had a hard time blending it to the mains easily, but I also never really tried to, just a simple pink noise calibration and away we went with the comparison, not the best way to do it.
Personally from an ease of use/setup the Axiom is a no brainer. We were able to set it down in any of our rooms, pink noise calibrate and it pretty much blended into the mains right away.