Yes, make your soundpack easy to uninstall though. And also, normally for turrets the directory would be portal/sound/npc/<something>. Anything that is located in the main directory of the game and is in the same spot as something would be in a GCF, normally it would be used rather than what's...
Not exactly sure if I understand your problem correctly. But here's what you can do: Try asking on the SRCDS forums as they are for SRCDS alone. Here is the link:
srcds.com forums
Well, it's not actually my map, it's a derivation of some sort, but I still mapped it ^_^. To the Portal_Playground_V1 map. You can download my version using SVN:
http://subversion.assembla.com/svn/portalplayground
It's called Portal_Playground_V2 and it's MUCH better.
Features
Energy ball...
you know, maybe they're forcing you to go to their ad sites (HL2.net) so they get can money from them, like, some type of script on the page redirects you in X number of seconds to an ad URL linked to their goole adsense/clicksor account. it can be done. :p