[Tex/LaTex] \ttfamily is too bold for me

Question

I use the following settings for my listings:

\lstset{
  %basicstyle=\ttfamily\tiny, % small
  basicstyle=\ttfamily\scriptsize, % middle
}

But the font in the listings is too bold for me. I tried a lot of things, but I couldn't change it.

I want to use a monospace (fixed) font in my listings, is there any other font I could use?

PS: I compile my tex files with a xelatex compiler.

EDIT #2:

Complete example:

\documentclass[12pt,german,a4paper]{scrreprt}

\usepackage{xltxtra}
\usepackage{lmodern}
\usepackage{fontspec}
\usepackage{xunicode}
\usepackage{listings}

\begin{document}
\lstset{
    basicstyle=\ttfamily\scriptsize, % bold and monospace
    %basicstyle=\scriptsize, % not bold and not monospace
}
\pagestyle{plain}
\begin{lstlisting}
cntNodes++;
nodes = (DG_NODE_ID *) realloc(nodes, cntNodes * sizeof (DG_NODE_ID));
if (nodes == NULL) {
    fprintf(stderr, "Error: No memory left!\n");
    return false;
} /* if */
\end{lstlisting}
\end{document}

Answer 1

scale down the monospace font or use flexible colums or define a smaller letter space (see package fontspec). SourceCodePro is part of TL2012.

\documentclass{article}
\usepackage{fontspec}
\setmainfont[Mapping=tex-text]{Calibri}
\setmonofont[Scale=0.95,
%             FakeStretch=0.8,
             Mapping=tex-text]{SourceCodePro-Regular.otf}
\newfontface\SmallMono[FakeStretch=0.8,
                       Mapping=tex-text]{SourceCodePro-Regular.otf}
\usepackage{listings}
\usepackage{lipsum}

\lstset{
  basicstyle=\ttfamily\small, % middle
  columns=flexible
}
\begin{document}

\lipsum[1]
\begin{lstlisting}
\directlua{securityproblem("\today")}
\end{lstlisting}

\lstset{
  basicstyle=\SmallMono\small,
  columns=flexible}
\begin{lstlisting}
\directlua{securityproblem("\today")}
\end{lstlisting}

\end{document}