PulseEffects - Limiter, compressor, reverberation, stereo equalizer and auto volume effects for Pulseaudio...
DFX Audio Enhancer - Formerly known as DFX Audio Enhancer, FxSound Enhancer instantly boosts the sound quality of the music on your PC.
PulseAudio Equalizer - Pulseaudio built with system-wide equalizer support. More information: http://www.webupd8.org/2013/03/install-pulseaudio-with-built-in-system.html
Letasoft Sound Booster - Boosts sound volume above maximum level
Hajo's Headphone Enhancer - Your Headphones, made more awesome!
Fidelizer - Feel the "Real Sound" with pure audio fidelity