Nice design - similar to what I'm doing for my basement build. After talking to Ed Mullin at SVS, I decided to place my subs directly on the concrete. I'm covering the opening in the cabinet with acoustic fabric. The sub I'm going with is the SVS SB13 Ultra, which weighs a cool 92 pounds. The cabinet will have a toe kick, but I'm thinking we'll install it after putting the subs in place. He also recommended making sure that the cabinet has enough space on either side of the sub to slide it into place. His final recommendation was to look for a sub from the outlet store - blemishes on the cabinet won't matter once it's concealed in the cabinet. Where are you in the process?