Enabling compression is easy. Use the following PHP settings:
zlib.output_compression = On
zlib.output_compression_level = 6
When you think about it, enabling compression and optimizing images could save a lot.
Ever compressed an image? Try it and see how bad images can be compressed. That's why I don't like on-the-fly compression. In many cases it's just a waste of CPU power.
Textfiles like stylesheets and javascripts however can be compressed very well. Enable UseGZfile and compress every stylesheet and javascript. Make sure the original files are kept, in case a browser doesn't support gzip.
Your URLtoolkit can be shorter by the way:
UrlToolkit {
ToolkitID = expires
Match .*\.(jpg|png|gif|css|js)$ Expire 1 weeks
}