I can't seem to get anything other than internal speaker out of Dosbox for this game. Seems to work fine with ScummVM, but their CGA emulation doesn't have the RGB option (when I retro-game, I retro-game).

The original EGA version of Police Quest only had PC speaker and PCJr/Tandy support for sound -- too early for sound cards at the time. To enable Tandy mode, you have to go into the dosboxPQ1.conf file and edit the line that says "machine=svga_s3", and change it to "machine=tandy" (without the quotes, of course). However, because the GOG launcher uses the same doxbox config file for both games, you'll have to change this back if you want to launch the VGA remake.

Aaah, gotcha! That explains it, because I couldn't find such a .cfg file in the EGA folder.

My assumption is that's the way the launcher was originally designed when Activision released the collection in 2006, as GOG tends to keep everything the way the publisher had it.

What I ended up doing instead of using the selection menu (which is a bat file I believe) was create two separate shortcuts, each using a separate DOSBox config file. Of course, this means not using the Galaxy client, as I believe it's hard-wired to use the selector. But for my purposes, it works great.