Given your room size, my concern is room filling volume might end up giving you the impression that your mains sound stressed. BTW, my little home theatre is virtually the same plan as yours; and, I can say for sure, my very efficient JBL L100t3's are not quite capable of delivering volume without some evidence of sounding stressed. If I wanted to fix my outcome, I'd need to spend about $15,000 on something like the JBL 4367's. At any rate, you might want to consider Klipsch all around.