Stick with the VP100. If your viewing space is 10x10, chances are you will be sitting relatively close. You will not need the VP150. If you are listening to surround music, you will likely not want to venture outside of the "sweet spot". If you simply want to fill the space with music, your mains in stereo should suffice. If you feel you need more, you might want to try for another VP100 (one over and one under your TV). If you have the space, you may want to use the same speaker as your mains for the best balance (though the best sound is achieved with all fronts at the same height).
