Dude i am no pro so you have me stumped. I have heard nothing but good things about the VP160. I dont have one but i have a large center i built using Axiom drivers, its a cross between a 180 and 160 , i am severely hearing compromised (tinitus) and i hear dialogue loud and clear. i would check and be sure all drivers are working correctly and get yourself an SPL meter so you can see what each speaker is putting out.
since you have a screen , how far away from the center speaker are you.Maybe share some pics .