This is purely a question of the volume setting and the position of the subwoofer in the room. As far away as possible from the wall shared with the neighbour.

As already written by MtCa, this is possible. You can find the manual on the Klipsch website. It also describes and illustrates how to connect it. https://assets.klipsch.com/product-manuals/Reference-Subwoofers-2021-Manual-v01_2022-05-16-135253_bdcg.pdf I myself have a sub right and left output on my receiver. One of the outputs is labelled "Sub (Mono)". I connected the cable from this output to the LINE IN LEFT/LFE subwoofer input of the R-101SW. On my receiver, I then had to set it to Sub (Mono) in the settings. This should not be necessary for you, as you only have one output on the Wiim Amp. Either way, it makes sense to read the manual for the receiver and the subwoofer. If necessary, you can also adjust other things such as bass level etc. on the receiver to get a good sound result. On my receiver, for example, I first had to activate the SUB mono output in order for a signal to come out. And then set the bass level and bass phase adjustment. So read the Wiim Amp manual to find out what settings there are for external sub-woofers.

No, no speaker cables are included.

Like any product, supply and demand.