Nick, yes that should work out well. Each pair of subs that are diagonally opposite should be as similar as possible. The diagonally opposite corner arrangement depends entirely on cancellation effects to minimize room modes. When the wave from one sub reaches the opposite one the sound at the mode frequency will be reversed in polarity and will partially cancel that mode frequency. A similar response of the subs at that frequency leads to a better cancellation when they meet their partner.
Maybe this is the route that I will go. I'll try another Outlaw sub and see how happy I am with the bass for a while. If I want a little more then I'll also add a pair of midrage ($1000 each or so) subs and arrange the Outlaw subs in diagonally opposite corners and the other brand in diagonally opposite corners.
