I am a bit sceptical.Got my 2nd hand LCD and very impressive I like these more then the LCD 4. The two LCD 4 I went through didn't have the low bass like the 3 does. It's very deep and vibrates the air inside sounding more like a subwoofer.
These almost do what you do with the 1266 by breaking the seal and increasing bass.
I tried the LCD-4 out of a TT2-MScaler combo and I tried two different LCD-3s as well. To me the LCD-4 had superior bass clarity.