In reply to:
is the soundstage wider with the VP150?
Not really. Just a fuller sound and greater power handling ability due to the extra drivers .
In reply to:
Any reason why the M22ti does not have a single midrange and a single woofer? Was it intended that the 5.25" drivers be best suited to mid and mid low and that the M22ti's are supposed to be coupled with a sub?
That is it. This is a reasonable maximum size for a bookshelf and while providing admirable bass for this size of speaker, it is intended that low frequencies are more efficiently handled handled well by a large enclosure (sub-woofer or fullrange M50 to M80 speakers).
In reply to:
Any particular reason for choosing the QS8s over the QS4s for the surrounds? Do they sound better (or perhaps rather, fuller) to you?
Personal preference. The QS8s have a slightly lower frequency response. This allows the subwoofer to handle frequencies from 70-80 Hz and lower rather than 85-90 Hz as would be preferred with the QS4s.
While some would debate that frequencies below 100Hz are non-directional, there are others that state that 80 Hz is the magic number. This likely becomes a personal preference of the final user. The QS8 guarantees that all non-directional information will be sent to the sub-woofer. For some users who have no directional hearing below 100 Hz, the QS4 will be more than adequate.
Again, this comes down to a user's perceived hearing and personal preferences. If the QS4s work fine, why pay the extra money on the QS8s if you don't need them, unless you're trying to compensate for something else?