Unsound - agreed on 40Hz, and even 20Hz at moderate levels in a moderate room with moderate music. I like the 20Hz 'sound' better than 40Hz, possibly because of the relative lack of low end phase shift, to which I am sensitive. The bass response effectively starts as low as there is program material. There are ways to successfully aid the bass against overload ie subwoofers, etc. I use an SS2 behind each main speaker, whatever model. In the Thiel passive XO mode they contribute only below around 40Hz (plus overlap), and there isn't much music down there. But nonetheless, that supplementary deep output provides local air pressure to aid the main woofer's room coupling. I'm surprised how much more authority the bass gains.
Please say more about 2>4 upgrade path.
My CS5 comment was market-based. And as you allude, most of that was self-inflicted, in my opinion. The product is good, especially the 'improved' version with Jim's driver designs. It's not common knowledge, but I consider the CS5 and the squandering of its potential segue into higher range markets to be classic self sabotage. The product as designed wanted a $15K (some said higher) price and another 3 months in development. Rather than settle into that league, Jim and Kathy were adamant about keeping it under $10K. It didn't 'fit' the market there. There was much too much speaker there to make sense, and its amp requirements etc. took it into the higher league anyhow. (Note that we had 100+ carte blanch firm pre-orders with no price stipulation.) You might detect my flabbergast these 30+ years later; this rant has never taken words before. One example of 'what happened' is that I had designed the baffle to include 3 stones (marble, granite & basalt) in 3 particle size ranges for an inert - extremely well-damped, good-looking baffle. The stone mix had enough variation and visual texture that the gel coat would be clear, to see into the stone matrix - all quite subtle since ground marble takes dye well. The casting molds required higher maintenance, and it would be 50% heavier, but what a baffle! I found the right supply partner in Atlanta and settled on $100 / each with quantity guarantees, etc. (Note that a company like WA might add $25K for such an element). I was elated. That is until I learned that Kathy came behind me, capped the price at $50, reduced the spec to ordinary bathtub cultured marble, and gloated over the cost reduction, all on their way to a $9300 / pair introductory price, which caused market confusion against the $15-$20K pre-marketing by distributors and dealers. End of rant.
It's called family business. The J&K alliance was internally infamous. They abandoned the CS5 platform and stated that it was 'too expensive' to sell through. I suppose polite professionals are supposed to keep such things under their hats. But I think that you fans might benefit from some leaks whose potential harm has long-ago elapsed.