Dark Gecko

I have possibly a dumb question. I have the upgraded Scion Navigation System, I had hooked it up myself quite some time ago. When I did install it I noticed a video out wire which I guessed was for the headrest monitors. Now my question is if it is infact for the headrest monitors do I have to use the insanely expensive Scion monitors or can I put any monitors in? I plan on doing the back three headrests with monitors and another in a custom sub enclosure I will be building.. Just hoping I actually can cuz I want all of it running from the SNS.