There's not really a standard to the rear speaker, people have used both di-pole/quad-pole or direct speakers. I think the perfered method is to use di-pole speakers. I would get the mains first, surrounds, center then sub. Possibly get M3's or M22's for the front and qs-8's at the same time. Then buy the M50's or 60's you want and move the M3's or m22's to the back. This way you get surround sound from the start, and you can go to a 7.1 setup instead of a 6.1. I've had both the vp-100 and vp-150, the vp-150 is much better sounding, I would wait and just get the 150.
I'm not sure about subs, still trying to deceide on it.
