usb audio converter surround sound?

I've got a 2.4 core 2 duo 20" imac, I'll use it as a music and dvd player and I want high fidelity surround sound on a budget.

So far my plan is to get:

http://www.trendsaudio.com/EN/Product/USB_Audio_desc.html

and a surround sound receiver and speakers,

But will the audio coming out of the computer go through the usb audio converter and into the receiver as dolby digital 5.1?

cheers for the help

The link didn't work so good but this will work for $20.

http://www.griffintechnology.com/products/firewave