It seems it is NOT correct to include the page number before the citation:
According to Ferris [2007, p. 166-167]: "To get an accurate indicator of commercial viability, don't ask people if they would buy—ask them to buy"
(Code: \cite[p.~166-167]{Ferris2007})
It seems we must include the page number at the end of the citation:
According to Ferris [2007]: "To get an accurate indicator of commercial viability, don't ask people if they would buy—ask them to buy" [p. 166-167].
How could I do it? I'm using:
\RequirePackage{natbib}
\bibliographystyle{plainnat}
Note: It is correct to use the same code to add that reference at the end:
(...) ask them to buy" [2007, p. 166-167]

2007also belongs at the end. Just write your citation after the quotation. Sorry. I guess I'm not seeing what you're after here. – cfr Jul 31 '14 at 23:32~(p.~166--167)after the quotation. – egreg Aug 01 '14 at 17:18As \cite{Ferris2007} said: "blablabla" ~[p.~166--167]. Do you want to write an answer? – chelder Aug 01 '14 at 17:43\citeauthor{Ferris2007}... \autocite*[166--167]{Ferris2007}. – cfr Aug 01 '14 at 18:41