The photo shoot and build for the S3X C4S has happened, but only Josh will have some clarity on when the manual will be finished.
While the impedance switch kit was a neat feature for the original SEX amp, we ultimately found that a lot of users of incredibly high efficiency headphones were setting the impedance switches for the highest possible impedance, which offered the highest noise floor, too much power, and an overly sensitive amplifier. We have since been more specific in the manual about which impedances we recommend and why. There are so few instances where the 16 or 32 Ohm outputs are useful that offering an expensive solution for accessing them didn't seem appealing.