How/What I need to connect speakers to my 360?

Well I'm still planning on buying a 360, and I don't own an HDTV (and probably will not for quite a while...)
So I've set my eyes on the VGA HD/AV cables. Now, I've read a ton about how to connect 360 to a monitor. Problem is, I don't have a speaker ON the monitor, I do have a speaker though, but am wondering how to connect it so that I get the sound. The White + Red cables that comes with VGA HD package cannot go in to my monitor, and I'm told to buy an optical cable.

So my question is, what exactly do I need (Links would be lovely too) so I can get sound and how do I go about connecting them?

Here's what I use:

Altec Lansing XA2021 (these are some of the best 2.1 speakers I've ever owned! I only paid $24.99 at Fry's Electronics)

It also comes with a R/W audio connect for the VGA cable.

Hope this helps you out.