There was some discussion of those towers in this thread (in case you haven't yet found it)!
https://forums.audioholics.com/forums/threads/ac4l-june-is-speaker-month-10-off-most.111464/#post-1252261
They do not specify the conditions for the frequency response they provide, however, it is a safe bet that the 20Hz bottom is not an audible reality. I might guess mid to upper 30's. The 6" drivers in my Canton Chrono 520.2 put out some good solid bass, so I think Canton would probably get good bass out of their 8" drivers.
As best I can tell, it looks like they took the old aluminium-magnesium tweeter from the GLS (and Chrono series) and put it in the newer GLE models (which were previously soft domes) when they eliminated the GLS series. I have heard this in the Chrono, and it is a nice tweeter. Maybe they dropped the GLS series because the GLE and it were converging on the same design/price-point?
Hopefully
@zieglj01 may be able to offer additional insight. I know he is familiar with the Canton GLS-2 and he may also be familiar with the tweeter used in the Boston Acoustics model..