Since installing Arch Linux and KDE I’ve noticed a delay after logging in to my PC (after log in but before the default welcome sound plays), after much searching on Google and the Arch Linux forums I came across a tip that certainly speeds things up.
All you have to do is delete pulseaudio.desktop from /etc/xdg/autostart
sudo rm /etc/xdg/autostart/pulseaudio.desktop
To be on the safe side, I would advise keeping a copy somewhere, for example
sudo mv /etc/xdg/autostart/pulseaudio.desktop $HOME/Downloads
You should then notice an improvement in startup time.