music frequency

Picking 40Hz means you will loose much of the reproduction of the bottom 7 keys on a piano and organ.

Remember that in general, a speaker that goes to 30Hz at 3db down will reproduce 40Hz notes clearer and more realistically than a speaker that goes to 40Hz at 3 db down.

My comments did not assume a sub, and it didn't sound like Odnok was considering one as well.

Yes, I agree with you there are compromises. One more you didn't mention is that the speaker with the higher cutoff will also probably be more efficient and require less power.

I am using a 4 way speaker (sub built in), where the sub goes to 18Hz. Granted, not a lot going on that low, but it's great to know that if it is present, it will get attended to.