asus realtek hd audio manager speaker fill

In the new Realtek manager I don't see an option anywhere for speaker fill which I hope will fix the problem if I can find it (because obviously speaker fill is all I'm looking for with playing music through the 5.1) but I have searched through every menu to no avail. I can hear the songs being faintly played through the rear speakers (at about a 1/10 of normal level in terms of volume, maybe even quieter, but it also has a significant amount of static noise that over powers the faint melody of the song). I have done the speaker test in Realtek and Windows system settings and all the speakers + bass played the sound at full volume and clarity as expected, but when ever I try and play a song through WMC or iTunes, it mainly gets played through the front left/right and bass. I have all settings in the Realtek audio manager, Windows system settings (I'm using Windows 7 64-bit Professional), iTunes (11.1.4.62), and Windows media center set to 5.1 surround sound (where possible) and the default optimal settings determined by Realtek (24Bits, 48 kHz) but neither WMC nor iTunes will play audio through the center or rear speakers (kind of). I have an ASUS Z87-A motherboard running the latest Realtek HD Audio Manager (6.) and I am trying to play sound through a new set of Logitech z506 5.1 surround sound speaker system. So I just set up my new computer but I cannot get programs to play audio in 5.1 surround sound, or even 5.1 fill for that matter. **Sorry about the length, I tend to be overly descriptive**

Asus realtek hd audio manager speaker fill