So Jeff, I called the city of St Charles today, and he did confirm that there are 3 new sirens and only those three, along with the T-128s, the 1 2001, and the 3 Whelen 4000s, which are all owned by the city of St. Charles. I also asked him about the T-128 that came down and he said that was from a hit-and-run driver that was never found. The siren was scrapped a while back....too bad because I'm sure it would have been at least some use. If nothing else, it would have been cool to have.
Frontenac has 2 Thunderbolts up, the one that you mentioned off Geyer and Clayton (visible from US 40 (when it's open)) and the other one is further south on Geyer before the first kink in the road. Here is a picture of the other T-Bolt (again, sun setting, not so great lighting)
I also found out recently that Kirkwood also had independent control over its T-Bolts and the one Whelen 4000 with the city. They are all set off with the county's tones, but just the ones within the city limits can be set off by Kirkwood PD is desired.
Uncommonsense, there is a 3016 on the West side of Suson Park, but about the same distance east, there is also a siren, C-1, which is a Whelen 4000 like you mentioned. It also happens to be a yellow one, which would fit the theme of the older ones being ordered yellow.
Jeff, as for the Whelen 2900s I mentioned in Lake St. Louis, those are actually Whelen 2800s of smaller size. You are right though in that the new sirens going up are all, if I recall correctly, Whelen 2900s. The one 2807 I saw was at Green Tree Elementary, but I'm sure there are more scattered around the city. As a note, St. Peters is also switching over its sirens to 2001s. At the St. Peters Golf Course there was supposed to be a Thunderbeam, but when I was there the other week, there was a 2001 in it's place. In the picture, you can still see the CD yellow box from when the T-Beam was there.
As for Nebo, IL....and all those other random small towns.....I really get around. If you ever get a Facebook profile, I have a Cities I've Visited Map that you can zoom into and see where I've gone. I update it whenever I do a siren drive to a new place.