There is directories you may have to dig through.
Theres one called "speakers" and another that I forget the name of.
The S8’s listening-window response (a five-point average of axial and +/–15-degree horizontal and vertical responses) measures +0.97/–1.90 decibels from 200 hertz to 10 kilohertz.
Paradigm Reference Signature S8 Speaker System HT Labs Measures | Home Theater
The F52's listening-window response (a five-point average of axial and +/–15-degree horizontal and vertical responses) measures +1.44/–2.37 decibels from 200 hertz to 10 kilohertz.
Revel Performa F52 Speaker System HT Labs Measures | Home Theater
The Synchrony One's listening-window response (a five-point average of axial and +/–15-degree horizontal and vertical responses) measures +1.18/–2.24 decibels from 200 hertz to 10 kilohertz.
PSB Synchrony One Speaker System HT Labs Measures | Home Theater
The 803D's listening-window response (a five-point average of axial and +/–15-degree horizontal and vertical responses) measures +1.90/–3.68 decibels from 200 hertz to 10 kilohertz.
B&W 803D Speaker System HT Labs Measures | Home Theater
There are some results (HT mag) which captures the 803d and the S8 v3. (The S6 will be the same but with less LF response).
In my eyes the B&W 803D is out of the question considering price and over 3db swing.
Another note is that you will want a sub for any of the speakers above as their THD gets higher during the LF, in fact a sub is welcome in ANY setup.