The Optical SPDIF is (laser) there's no power, the laser is powered off the 24-pin MOBO main, and you need a 'Toslink' cable -> e.g. cheaper 6' http://www.newegg.com/Product/Product.aspx?Item=N82E16882203119
The SPDIF doesn't need to be connected to the GPU, however IF you use an HDMI (video & audio) connector then you'd need to loop back an 'audio' connection to the Z-5500. So use an DVI -> Monitor and Optical MOBO -> Z-5500.
Otherwise is the 3mm connections, right, (1x3) and (1x3) as shown above; Front/Rear/Center. The quality of the speakers you'd never hear the difference.