You are right, there are a few criteria.
1. I am not talking "most" systems. I am discussing excellent systems. Many average Joes probably won’t care that much though. But it is important to others.
2. I am not considering bumping the woofer’s Qts above 0,707 in order to artificially boost the system’s low end response. The problem with that is a phase deviation, bloating, or even synthetic bass (RCA Radiotron Designers Handbook, 4th edition, 26+ engineers). And can one ever really obtain flat response with such a measure?
3. Another problem is that dbs add. By that I mean each components deviation is additive. If we have three components, we add the db variation of each. For instance, -0,2db plus -0,15db plus -0,2db gives us -.55db from flat. A deviation varies vs frequency, and exists over many octaves. (RCA Radiotron Designers Handbook, 4th edition, 26+ engineers explains this plus the next paragraph.)
Another concern is if we limit the bass response, we also need to limit the high frequency response. Visa versa as well. (RCA Radiotron Designers Handbook,)
We need to keep each component’s frequency response as flat as possible, minimal deviation to protect the musical information.
4. I am discussing capacitors in absolute sonic terms (not measurements), so as to not cover over another fault in a poor/average design. The capacitors I am talking about are not a 716P orange drops.
5. Every time one compromises sonic quality in a part, a stage, in a component, the synergy will not be as optimum as it could be. Design and parts quality is very important.
By the way, imo, -3db at 23 hz is extremely poor frequency response unless one is purposely constructing a high pass filter to limit the bass response, which is useful for certain purposes. Cheers