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.

not personally, depends entirely on whether you think you have enough bottom end, nothing else..

45hz could be adequate for most music if the frequency response is flat at 45 hz and started to roll off at that frequency. I doubt that it is but you must factor in the roll off when doing comparisons. Some speakers that say they go to 45 hz actually start to roll off much higher and you would certainly need a sub for decent bass.

Also consider what 35hz really means as well.......

Also consider what you might accomplish, bass wise, by placing your speakers to take advantage of bass nodes in your room.
 

FWIW