modules and configuration

[Brian Barr]

I have two questions

In general:  Is there a good location that describes how modules get loaded at boot, and how to configure which get loaded when?  

I see there are several locations that "work" on modules and the ordering and importance of each is lost on me.  Locations such as:  /etc/hotplug
/etc/modules.conf
/etc/modprobe.d
/etc/modutils

all seem very intertwined.  If I understood the process I could work out a solution to my next question...

In specific:  I have an nforce board with on-board audio, as well as a PCI sound card (snd_cs46xx).  How do I disable the on-board audio?  I have managed to set xmms, mplayer, and xine to play through the PCI card, which is card 1.  However, I can't quite find how to convince firefox plugins (mplayer-plugin, vlc-plugin, or flash...) or rhythmbox to use anything but onboard audio (card 0).

Thanks in advance.