Greetings Pklin,
The reason I chose the QS4s was because when I talked to one of the guys at Axiom on the phone, they said there would probably little difference, the big difference being that it is rated to handle more power. But, how often are most of us actually going to use that power. Being that my room is like 13x24x9 and I am only using about 13-14' of the width of the 24' I find that it is plenty of power. Plus, another reason is because the fact that I had to buy two pair of QS4s meant I had to keep it within budget. I couldn't really justify buying the QS8s for roughly 300 more total, over the QS4s.
Now for the VP150, I decided on that one because I heard it was a wider sound stage and better seemlessness when panning across the front. I also heard that it was clearer than the vp150. Of course all that probably is slight/minimal but I didn't want to say "What if" and have to upgrade.
Regardless, either of the speakers you choose most likely will put you in a very happy state. You really can't go wrong either way you choose.
Anyway, I hope this helps.
Regards,
Jon
