@joemendel From what you're suggesting, it sounds like you want to use channels that are not used for actual sound output from the game/Windows. You may already know this but you need a second sound card to run tactile units from, separate from game audio and Windows audio output.
So on your second sound output device, you would buy 2 of those cables you showed previously, plug one of them into front L/R out and the other into rear L/R out. That will give you 4 channels of tactile, one for each BK unit. Be sure to select 5.1 or 7.1 output in Windows sound settings also.