Hello, you said "Can I get by with one sub or is a stereo pair truly necessary. My monitors go down to 38Hz – is that “40Hz range” crossover point low enough provide a seamless integration (i.e.: will I be able to tell where the sub is when it “kicks in”)? How difficult is placement? General pros/cons…etc…?"
One sub works , especially when crossed over low for music. There is no stereo signal that low. Crossover below the main speakers 38hz, try 32hz so the sub does not interfere with the purity of essence of the monitors. For seamless intergration do the sub crawl (place sub in the listening position and move yourself around the room, while listening for the most even bass). Do this and you can't go wrong. No downsides just intergrated bass with extension dow to 20 hz flat.
One sub works , especially when crossed over low for music. There is no stereo signal that low. Crossover below the main speakers 38hz, try 32hz so the sub does not interfere with the purity of essence of the monitors. For seamless intergration do the sub crawl (place sub in the listening position and move yourself around the room, while listening for the most even bass). Do this and you can't go wrong. No downsides just intergrated bass with extension dow to 20 hz flat.