Center channel placement is critical, as it is in all speakers. As long as the center points into the listening position you should be fine. I'm told the difference between the 100 and 150 is the 150 is more dynamic, having a larger enclosure and more drivers.
I've been talking to Axiom regarding my center channel choice. I was interested in the VP150 more as an addition to my current setup, which they assured me would be a good match. However, we have also been discussing using a pair of M3's wired in series as an alternative. These would provide as good as center setup, or better, than the VP150. My only concern is what that would do to the ohm rating? Running in series, or parallel, two 8 ohm speakers would make it appear as a 4 ohm speaker!? Since my AVR is rated for 8 and 6 ohm I assume that the center will work the amp much harder creating an possible overheating issue. Fine for short durations but maybe a problem over extended periods. I'm still investigating and have sent an email to Pioneer for clarification.
