Setting up 3 VP100 vertically or 2 VP100 vertically and the center horizonally would definitely work. I would cross them over to the sub higher than the suggested 80hz since they will not have much bass extension. Start with something like 100hz and keep the 500 up front with your mains. Even better would be something like dual EP350's matched up with the VP100's - one sub next to each L & R speaker would work wonderfully with a higher crossover point.

I’m armed and I’m drinking. You don’t want to listen to advice from me, amigo.

-Max Payne