You should use apt-spy. It can benchmark debian server for you. I use these parameters:
Code:
apt-spy -d unstable -a North-America -o mirrors.txt
man apt-spy is a good place to start. DO NOT use -o /etc/apt/sources.list or it will overwrite your current sources.list file! You can do:
mv mirrors.txt /etc/apt/sources.list
then add any other sources you may have
OR
Simply add the new Debian mirrors (from mirrors.txt) to your existing /etc/apt/sources.list. Whatever works for you.

Pay no attention to those who are whining about apt being broken as they are unenlightened.