It actually depends on your drivers. For instance my Realtek HD codec/drivers for my onboard gigabyte board has an option to separate the front audio out from the rear, or let them both play the same audio, or mute the rear as the front is connected ect. Now here is the ****ty thing on my end, if I use digital out (through the rear) I have no ability to use my front audio out. In my case this is a problem because I use TOSLINK (rear) so I have no front audio. The problem also occurs if I use Digital Coaxial so don't think it is only a TOSLINK problem. If I want to use front audio I first go into my Realtek Contol panel or whatever, and disable digital out, switching it to analog, then my front audio works again...
Anyway, I might have not answered your question, but I hope I was able to give you some insite.