I own the cs3.7's and don't miss the bass below 35hz but I don't listen to pipe organ. With respect to a sub, Thiel's smart sub system is amazing. It does far more than "add bass". In fact, adding much bass to a well broken-in and well-fed pair of 3.7's in a moderately sized room would be overkill, IMHO. The smart sub gives you more placement freedom and can make the sound of your system more effortless. I wouldn't even consider a non-Thiel sub with the 3.7's because none will sound seamless. Many people have heard my current system and while it had its flaws to be sure, no one has ever commented on a lack of bass...in fact, most are surprised by how strikingly musical the bass is. Nonetheless, having heard the SS 2.2, I wish I could afford a one but I'll have to save up first.
