Modules from /etc/modules are loaded by /etc/init.d/modutils which is
symlinked to /etc/rcS.d/S20modutils. If you want to have your script
run before that, symlink it to /etc/rcS.d/S??modutils where ?? is less
than 20.
If instead you used update-modules to add a line
alias sound-slot-0 modulename
to /etc/modules.conf, the driver will be loaded when needed.
By the way, are using kernel 2.2 or 2.4? 2.4 has improved isa pnp
support, /maybe/ you won't need to run isapnptools.
best regards
Andreas Janssen