I am new to building an HT....I am about to build one in my basement and based on the columns the room will be roughly 10.5'x18'....I plan on doing 'staggered' walls. Should I do it on all four walls (two walls are against concrete? Should I construct the door the same wall? I plan on building a stage (with sand in it) onto which I will put the bass. That being said do I need to but down a subfloor (on u-boats) between the stage and the risers?.....thanks for any help you can provide.