Shake IT - nothing coming through Rear output

Just got my bass shaker setup which consists of:

4 x Reckhorn BS-200i Bass Shaker

1 x 800w Amp

I’m running 2 x RCA cables from the front & rear output on the motherboard sound card and run them into the Line 1 & Line 2 input of the amp.  

When testing the speakers through windows & realtek in quadraphonic mode, all is well, however in SimHub the rear output isn’t outputting at all.

Am I missing something?