Firefox and Mozilla helper applications

[BBBB]

I am using Dapper i386.

I would like to play streaming audio in Firefox.
The link goes to a .pls file which I believe is an .mp3 playlist file.
When I click on the "Listen" button on the web page, I go to a blank page.
I do not have an application listed in my Download Actions setup for .pls or
.mp3.

When I am using Mozilla web browser, Beep Media Player opens up and plays
the
stream without a problem.

How can I get Firefox to open the stream with either Beep or XMMS?

Thanks,
Bradley