Sure!
It is a DC controllable pump with 1300gph Max flow and 12' head height (i.e., flow won't decrease easily with increased pressure). It's extremely quiet, but...


So, yeah, dropped some coin on a ultra quiet german return pump for this tank, but that wouldn't have been needed for a smaller tank... This tank is just big enough that the Eheim universal AC pumps I like (and which are bullet-proof and relatively cheap) wouldn't do it.
The DC pumps are tricky because they can be quieter than an Eheim in a raw decibel sense, but the sound can be much less... organic? The Eheims have a hum that is pretty quiet after they break in and which doesn't bother me at all. I have an Echo Tech Marine DC pump in the living room for example that is 'quiet' but the sound it does put out is pretty high pitched and not my favorite.
As for its placement - the pump is immediately after the canister (on the canister out) and will be right before the reactor. The reactor will then go to the sterilizer which will go to the heater which will go to the hard pipe return line. There are a few reasons for that placement. First is that canister keeps debris out of the pump. Also, the pump in the FX4 is in the bottom of the canister (rather than in the canister head which is more typical), which makes priming the system super simple. To start up the system from scratch I have to fill the FX 'bucket' with water and turn it on. It pumps out the entire contents of the canister before it starts sucking wind, so it starts the syphon on the intake line without me having to do anything special. Once the air is mostly out of the line I can turn on the booster pump and turn off the FX. This placement also allows me to generate some pressure in the reactor which is useful for dissolution and keeping the noise down.