I have a room that's roughly 15' x 20' x 8'. My current setup is a set of RM95 speakers with a denon 1910 receiver. I want to upgrade my sub from my 8" Yamaha. I am also going to be upgrading in the next 6 months or so to a pair of RTiA5's and a CSiA4 center, keeping my RM95's as rears. Which should I go with, the PSWi225, or the DSW Pro 400? OR, do I need to go even bigger, say with the DSW Pro 500 or 600?