Welcome to the boards and congrats on the system. You should only possibly notice a timber change when running pink noise. With all other material you should be fine. I would really look into playing with the placement and checking that all of the driviers are working on the VP150.
I've had mine above the TV, above the TV by 2' and below the TV in front of it. The Vp150 is versatile and can be flipped to aim the speaker flat or angled up but you still may need to use some shims or door stops. To me the best results I've had is directly below my screen in front of it.
The last thing to check is that your system is balanced properly and that you do not have any settings engaged on the receiver that may manipulate the sound.
Good luck.
