I've had this idea month ago as i use both headphones and Hifi Amp as output for my PC, and they respond in a totaly different way to the frequencies. So, i wanted to suggest to integrate an equalizer in pulseaudio as it's going to be THE sound server ;) ... I also thought about the ability to store different equas to be able to switch easily between hardware output! (for example buit-in speakers and headphones on a laptop.)
This idea is being discussed in Ubuntu idea pool, see here:
http://ubuntuforums.org/showthread.php?t=483331
P.S. i selected libpulse as concerned component, but as i don't know pulseaudio really well, feel free to select the right one ;)