3.5mm connection vs optical out quality difference

I have a Dell Inspiron 9300 laptop and a Logitech z5500 5.1 system.

I recently purchased a turtle beach audio advantage micro which allows my laptop to output optical signals direct to my system. I know this is ideal for playing dvds and games that support dolby digital.

but if i'm just playing normal mp3 files on my winamp, will the quality be better or louder than my original cheaper setup of just using the standard laptop audio out (3.5mm).

The turtle beach external usb sound card does re-encode signals into higher 192kbs but my mp3s are usually pretty high quality anyways, does it make a significant difference to justify spending 30 bucks on this usb sound card?