I've treated rooms I've used for home recording studios for years, and worked in pro studios ad nauseum. That said, I'm firmly in the "no treatment needed in the hifi room" group...I like the ambient sound of a "living space" room, and find all I need to do is own normal furniture and move speakers around a little. My system sounds great, has standing waves here and there but not in my listening spot, and the bass is tuned by careful listening to a REL sub. When I record stuff and put it on in the "untreated" space, I hear it differently and that's a good thing.