But actually the LCD2 is very efficient at 91DB that would be considered not difficult to drive as you also said they did work on the CSP-2. Actually the D7000 I just switched to tubes the main difference I see is a little less sound stage but it is more transparent. I guess more than one amp is always a good idea.
Hmm, but in my book 91 dB is not very efficient. A lot of headphone run much higher than that, like 100+ dB/mW.
Good idea is more than one amp :D it means, "I agree!!!"