That is one fried tweeter, LOL. Nice speakers otherwise though. My guess is that you can replace it with like and it will be fine; probably a hidden defect. How much T-M and of which type did you do on the tweeters themselves?
I've caused a couple of tweeters to fail in my lifetime (and some woofers - Here's looking at you, Wharfedale) but usually due to running high volume content with distortion on a low to medium powered amplifier. Last one I remember was a Paradigm of some kind using an Onkyo integrated amp.
What's that LP propped up on the left tower? That's some interesting jacket art! Also, if that's "Morning" (Phase I think? - I always thought it might be a play on words "Mourning Phase") down there on the floor, we seem to have similar taste in music. That album will test your woofers for sure.
P.S. yeah I really quite like the S400 v.1s and I hear they've been improved in the v.2. I'd also like to give a listen to their active versions, but it's so hard to actually find an audio showroom these days and $2K+ is a lot to shell out even if you can return it free. BTW, I had always thought that the woofers on these things was made by Scanspeak. Guess I was wrong.