"One question concerning 4 subs - How are they connected to the amp?"
The amp I supply with the Swarm is the Dayton Audio SA-1000, part number 300-811 at Parts Express.
It has a single channel of amplification but two sets of output binding posts wired in parallel.
The subs are connected in series-parallel, such that the four 4-ohm subs present the amp with a 4 ohm load.
Two subs are connected in series (via binding posts on the bottom), forming a two-sub "series string". Then the other two are also connectged in series, forming a second two-sub "series string". Then the two "series strings" are each connected to one of the sets of binding posts on the back of the amp, which puts them in parallel with one another.
Going into a bit more detail, the first sub in each "series string" has two sets of binding posts. One set is connected to the amp, and the other set is connected to the second sub in the "string", which only has one set of binding posts.
So you’d need four sets of speaker wire: Two sets go between the amp and each "first" sub of a "series string", and the other two sets of speaker wire go between the "first" and "second" subs of each "series string".
Some people use two amplifiers, typically one for each series-wired string, for a bit more flexibility.
"Stacked spades/bananas? Seems like a lot of hardware to me."
No stacked spades or stacked bananas.
I guess it’s a lot of speaker wire. Unless the runs are really long, sixteen gauge wire works just fine. You end up with the equivalent of thirteen gauge wire because of the series-parallel topology.
Duke