Sorry it took so long!
Starting with the soundcard (I presume you've got the drivers installed).
I've got the 'front out' on the souncard connected to my amplifier.
'Rear out' is where I've got the headphones.
Now going to the configuration menu in Cross:
The device is set as ASIO4ALL v2. You'll then need to click on the 'control panel' button next to this selection box, which should bring up an Asio4all box. Click on the spanner in the bottom right corner for advanced options.
Click on the button to the left of 'USB Multi-Channel Audio Device' - it should light up with a little triangle. Now click on the little box with a Cross inside to expand this option - make sure that 'Out: 8x 8-96KHz. 32Bits' is lit up.
That's it for Asio, so close it. You should be back to the audio settings.
On the outputs, select as follows:
Output 1: - Audio Device 1/Audio Device 2
Output 2: - Audio Device 5/Audio Device 6
Check that Routing Mode is set to Dual Stereo, and that Output 2 is set to Cue on the diagram and you should be good to go!
Best of luck - I hope that this works.