Wilson Benesch ACT

Has anyone had experience with this speaker. To be used on a Modwright KWA150 poweramp

Is the frequency response flat through the midrange

One of the most beautiful speakers to look at out there IMHO. I tried to audition them when I was in the hunt to no avail--could not find a dealer that had them on hand anywhere on near where I live. I did manage to hear the smaller two ways (cannot remember their name) which share some design characteristics and found them lean, dry and uninspiring. Not sure if the same can be said for the ACT's however.
heard a pair about 8 years ago though in house audition at local rep. Extremely fast and transparent, and very articulate bass, not to mention incredibale aestetics.
Nothing to compare them to, no 2nd habd market, probably problems with service - buying these speakers would be a big leap of faith.
I have heard them a couple times at my local dealer (who loves them and wants me to like them too), but I find them unlistenable for more than a few minutes. By my estimation, it did sound flat through the midrange (and higher), but that is what I didn't care for in them. It just sounded like pins and needles in my ears after more than a few minutes. But it was one of the most neutral and revealing speakers I've ever heard.

In all fairness, I find some other speakers a bit on the shrill side that others don't, so this as much a reflection of my tastes as of fact. If I were listening exclusively to vinyl and had a nice warm tube amp, I may feel differently about them.
I found them fatiguing as well, which the dealer said he had never heard that before. I will say that the build quality is exceptional and they look absolutely fantastic. I really wanted to love them as the aesthetic was exactly what I was looking for. Oh well.
I had them for 6 weeks. They are not to my ears fatiguing. They utilize a silk dome tweeter which if anything is on the soft side. They are ,however, very neutral which may not be to everyones taste.
I owned the WB ACTs for over two years and found them on the warm side with a golden midrange and balanced frequency response. The bass is smooth and provides a nice foundation but lacks attack and low range oomph- I ended up buying the WB Torus infrasonic generator to pair with the speakers. The ACTs were also fairly transparent to the source. I've owned Kharma, Genesis, Wilson (Watt Puppy series), Verity Parsifals as well as numerous other speakers and would put the ACTs in the middle of the cold-warm spectrum with Kharma and Wilson leaning toward blue and Verity and Genesis leaning toward red.

Gear was mostly solid state, Class A amps (Lamm tube and hybrid) and Esoteric digital. If you find them fatiguing, check the gear that is driving the speakers and compare with your own setup to see if that is the issue.
I think these comments really do prove the adage that you have to listen for yourself. Where I found them a bit sterile and sharp even on tube amps (Manley snappers, ARC VSi 60), Classicjazz found them warm with solid state. Maybe his use of class A amps is the difference, which could also explain why he found the bottom end lacking oomph.

What a crazy hobby.
I own them and love them. Edorr describes them well. They are fast accurate, transparent, tight ( but not real deep) bass. They don't inject a lot of warmth into the music (may be because of the carbon fiber cabinet) but the instruments separate out in space nicely so it doesn't sound like the music is coming out of a box. Also, they are extremely revealing of what is upstream. That being said, I can see where some can find them dry, uninvolving or edgy. I get a rich tone and warmth from my analog rig and 300B tube amp, along with the speed, accuracy and coherence of the speaker. That works for me. I can listen for hours.
Be careful with what you pair them with. I can see where they may not work with some gear.