Welcome to the forum TheFactor
For surround duties I would go with the QS4's or the QS8's. Looking at your room either would work. The difference between the 4's and 8's is the 4's have dual 4" drivers while 8's have dual 5.25" drivers (they both use the same tweeter, dual 1" tweeters). The 8's have a slightly better frequency response and can handle more power to fill a bigger room while the 4's are designed for small to medium sized rooms. Like Jakewash pointed out the quadpolar design allows the listener to hear and feel more immersed in the sound as opposed to directional sound that you would get with a using a pair of bookshelf speakers.
Good luck,
