Supe, welcome. It's safe to say that horizontally positioned VP150s would be a significant improvement over your present arrangement, even if they're not ideal main speakers in that position.
Alan's reference to using VP150s vertically as mains reinforces a point he's made before. Although I'm not personally familiar with the VP150s, the result certainly isn't surprising. Favoring a vertical center where possible has been frequently suggested, including turning a VP100 on end to experiment with that positioning.
