Ubuntu karmic uses pulseaudio as its audio system and if you have a good quality audio card,you can enable surround sound and use equalizer to make sound quality better.
1.First,the installed pulseaudio version is 0.9.19 and need to update to 0.9.21.

Just add “ppa:ubuntu-audio-dev”(without quotes) as a software source in System -> Administration -> Software Sources->Other Software.Reload and it will automatically add the correct PPA and it’s GPG key.(Thanks ARSENDY for the comment)

update and install pulseaudio:

sudo apt-get update
sudo apt-get install pulseaudio

you can use this command to check the pulseaudio version:

pulseaudio --version


Goto System->Preferences->Sound -> Hardware,select your audio card,config->choose Surround or digital output

3.Download the equalizer package from attachment and install it:

sudo dpkg -i pulseaudio-equalizer_2.4_all.deb

you may need to install some dependences which will be list in the output of above command,just use sudo apt-get install package_name to install them.
4.Open equalizer from Applications->Sound and Video->PulseAudio Equalizer,this is a
15-band equalizer.Enable equalizer and set on it.