single-spaced quotes within double-spaced document

[James Lindenschmidt]

I have a book-class document that is double spaced, set to give single-spaced 
quotes. To accomplish this, I have the following in my preamble:

        \renewenvironment{quote}
                {\begin{spacing}{1}\small \list{}{\rightmargin\leftmargin}%
                \item\relax}
                {\endlist\end{spacing}\noindent\hspace{-0.333em}}

However, I would like to increase the amount of space between the 
single-spaced quotation and the double-spaced, standard text. I tried using 
the following:

        {\setlength{\parskip}{2ex plus 0.5ex minus 0.2ex}}

But I couldn't get it to work. (note: I don't know if I want 2ex, I just used 
that number to see if I could get the spacing to change. It didn't).

I know virtually nothing about LaTeX commands, can anyone help here? I'm in 
over my head here.

Thanks,

James Lindenschmidt