Did a quick analysis here:
https://amcoustics.com/tools/amroc?l=550&w=427&h=275&r60=0.6
Your speakers and listening location are not ideal due to the modes that will express most strongly at the ends of the room between 30 and 70 Hz. The location of your library/desk area also limit bass traps to the ceiling and far wall, so whatever you use it has to be super effective per square foot.
If possible, move the speakers further out into the room. At least twice as far.
Start with floor to ceiling GIK soffit traps in the area behind the speakers. This should help a great deal. If that’s not enough add soffit traps across the top and bottom of the far wall. You can also consider using monster traps there as well.
I don’t think you’ll need the range limiter unless you also feel your system starts to sound thin after the soffit traps. If that’s STILL not enough you’ll need to put soffit traps from the top of the traps behind the speakers to the edge of your bookshelves.
https://www.gikacoustics.com/product/gik-acoustics-monster-bass-trap-flexrange-technology/