Sound font troubles in GB '11

I've tried to install sound font (sf2) files into the OSX/Library/Audio/Sounds/Banks folder so I can use them in GB '11 with my MIDI keyboard. When I try to move the sf2 files from the 'Downloads' folder to the 'Banks' folder, I get this message: "The items can't be moved because Banks can't be modified" and two options: "Authenticate" or "Cancel". When I choose "Authenticate" I'm asked for my admin password and the files are moved. I can see them in the "Banks" folder. Then I create a new software instrument in GB, go to the 'Edit' tab, select DLSMusicDevice, click the 'Sound Generator' button and in the window where the drop down menu is, I only get two options: "QuickTime Music Synthesizer" and "User define bank". I've downloaded several sf2 files (including violin, didgeridoo, trumpet and a sitar), but none appear on the drop down list. When I select "User define bank" the instrument sound I get when I play a key on my MIDI keyboard is the single violin. I'm downloading the files in unzipped/non-compressed format (sf2) and from reputable sites. Am I downloading and moving the sf2 files correctly, and if so, how can I select them in GB '11? Everything I've looked at online says that once the files are moved into the "Banks" folder they should be seen on the list in the Sound Generator editor window, but mine aren't there...

Please help.

Cheers.