Frequency Response

No and no but that’s just me.

There’s been many threads about using multiple subs in a DBA (distributed bass array). You might want to look that up. There’s also digital means of integrating the sub/s into the system, to help it be more seamless. Not seem less.

As there is still quite a bit of information in that region and below. You’re going to miss out on the development of the full spectrum found in most music that has any percussion instruments.

Giving a more specific answer would require more information, like room size and dimensional ratios, transducer type used, and there’s no definitive answer here on always using a sub.
Even for a stand mount 45Hz seems a little light in the bottom end (especially in room), why did you choose the particular loudspeakers you’re using?

@rixthetrick - I am pondering speakers that go to 45Hz - I haven't heard them live yet but I like the design.  My current speakers go to 35Hz - so its just a thought.  As always in this hobby - you have opinions on both sides of the argument.  I haven't used my ears yet to make a decision but thought it might make for a good discussion.