There is no free lunch when it comes to frequency response. If you try to reproduce the lower frequencies with a driver that you are asking to also reproduce the midrange frequencies with, you will muddy up the midrange (it is doppler distortion which is a function of physics). The problem is worse using a high Q driver because of its weaker magnet. Thus, it is much better to keep the lower frequencies (below 100 hz) out of the midrange driver and biamp to keep those frequencies out of the amp as well.

Linkwitz tried many drivers and concluded that OB sound is best with drivers with a Q of 0.4 to 0.5. It is a function of damping (even though that Linkwitz used SS amps, not tube amps). I am sure that the Silver Iris drivers sound good, but if your goal is only good sound, then you're done (and you may not care about the midrange distortion, which is fine too). But if you are after great sound, then you really need to be looking elsewhere.

Retsel

I suspect these are speakers that would not test well, especially at high levels with bass rich program material, but which sound very appealing at moderate levels. Only an audition will tell, so who's going to bring a pair to the Lone Star Audio Fest next May?

Regarding the stamped versus cast frame, cast is better, but it's also more expensive. The Silver Iris with a cast frame would be be quite a bit more expensive, and out of the reach of people who are now enjoying it.