Just got a Dell Inspiron 580 with integrated 7.1 audio output. Not sure the chip set. Headphones work from the front audio jack but my speakers won't work from any jack. Speakers are Boston Acoustic BA 735 digital speakers w/ subwoofer purchased Dec 2000. Why would these not work with the new computer? The old computer used a Soundblaster Live with Digital Audio output card.
Unfortunately your new Inspiron 580 does not have coaxial output.
As such, you will either need a new sound card that has a coax output or new speakers.
I would highly recommend getting a new set of speakers.