I have the XXLS400 FF IN A 4x8 metre room, I have no neighbours to worry about so can let it run free. Honestly I thought I had done myself an injustice not getting the monolith. But the 400 is epic. There are snippets of films I still think damn I wish it could hit slightly lower. But that's a rarity. It can induce serious amounts of grunt with ease. More than enough for me., and I love the lows. It's clean and punchy and goes seriously loud, and my Windwos get a serious workout with it at reference level, it's awesome, get one :0)