I understand what Mr. Green is getting at here. The O2 MK1 has some qualities that the LCD-2s and HE-6 just cannot touch. At times, it truly is a matter of technical ability rather than preference. It's important to note though that you can get the LCD-2s and HE-6 up and running close to their potential for just a thousand dollars in amplification.
The O2 on the other hand is hard to source at a reasonable price. Their amplifiers, even harder.