I owned the Q700s for a while, key word being owned.
IMHO, when used with subs, they don't really offer much over the Q300s. The 2.5 way design means the UniQ driver is doing the bulk of the work, with the dedicated 6.5" woofer kicking in only about the point where you'd be handing off to the subs anyway. I also appreciate the added flexibility of a ported design, as plugging the ports on my R500s made a difference for me in getting the crossover region with the sub right.