I've got the front and back audio connectors working simultaniously on my Motherboard (Gigabyte GA-EP35C-DS3R) with Realtec drivers.
Activate the 'Mute the rear output device when a front headphone plugged in' under the advanced settings menu.
Click on Folder Icon next to Analog. Click on the 'Disable Front Panel Jack Detection' button.
I've got both green connectors set to headphone.
Only the 'Speakers' icon is showing....no '2nd Output Device' is showing.
It has always worked for me.