For one, it isn't necessary, if I can get reference level output in a 2000 cu ft room with a 50hz xover using the smaller 250c, the larger one will certainly be just fine.
Second, it's too easy to localize subs past 80hz, and actually, I was having some issues with being able to localize my sub at 80hz until I added a second one on the opposite wall.
Third, above 60hz, unless the sub is placed along the front wall with the LCR, the path length differences at 80hz can be large enough to cause uneven responses around the room at the xover point. An 80hz wavelength is 14' long, above 1/4 wavelength, or worse even, 1/2 wavelength difference, there will be areas of cancelation.
Using multiple subs can largely solve this problem, but AFAIK, op doesn't have multiples.
Personally, I am if the opinion one should use the lowest xover permitted by room acoustics and speakers possible. This is coming from experience.
Sent from my LM-X210(G) using Tapatalk