I think you should turn your subs around, put that amp plate behind the sub box, and seal the trunk off from the cab (with the subs in the cab part). This will increase bass output.
But I like the amp-rack/stand-thingy. Although you should think about moving it. The carpet + the size it is and where it is, is probably lowering your audible output. The carpet naturally "absorbs" waves. So, even still, having something nearly blocking off a big part of the opening into your cab is gunna dampen things.