those 1/8" audio outputs are stereo line outputs and will need something like this:
https://www.monoprice.com/product?p_id=666
or this:
https://www.monoprice.com/product?p_id=5598
See page 1-22 of your MOBO manual. The lime/green jack outputs the left/right channels. This is likely going to be lower than SoundBlaster audio quality (which is fine if you are just running basic computer speakers or don't care about audio quality). I think that old Sony processor you have is still going to sound a whole lot better.