A good alternative bundle if you want an amp with Bluetooth is this one: https://petertyson.co.uk/rotel-a11-tribute-integrated-amplifier-with-q-acoustics-3030i-bookshelf-speakers When I got my Dalis, I chose the Rotel bundle over the Marantz bundle because of the Bluetooth. It doesn't have recorder outputs or digital inputs (they buzz on the Marantz anyway!), but you may not need them. The bundle also comes with a better set of pre-terminated speaker cable.
Btw for the more technical questions I'd recommend just emailing Q Acoustics, they respond really quickly.
Yep you don’t see many other speakers brands rated this way. It’s more normal practice when quoting frequency responses just to give the -3db frequency.
It's almost pointless to say 46Hz between -3dB and -9dB, that's why no other manufacturer rates this way. I know why they've done it though, so the 46Hz will be a selling point.
I think they mean the -6db point (drop in bass output) is at 46Hz with a variation of +/- 3db. So -9db to -3db at 46Hz dependent on setup (port bungs etc.).