alot of the protocols are left over from years past.
they had a purpose then..and some do now actaully.
then there are some programs which still rely on them.
esd, nas, poly.. are some of these protocols.
then came arts (for kde mostely).
then came oss the last few years.. it was to solve alot of the crosstalk-- so to speak amoung the different systems.
now comes alsa.. again, to do the same things all the others were.
my suggestion in general is to use gnome, put ALL the sound systems you can find on your puter..
then use oss for input and output--- unless you have a proven better reason to use another.
make sure alsa is installed, but only have " asla-utils"
and "oss-preserve" on at boot time.
remember some programs will call up esd or arts when necessary.
and some programs like vlc will require that you shut down your 'sound server' (ie that thing-ma-jig that allows for your 'system sounds' (ie the little beeps & boops while you are working).
good luck man