This is a pretty late comment, but I recently got some AD700s. I don't understand people saying they don't notice a difference after amping them. I question whether SOME of those people have actually tried that or made that determination based on theory, being that the AD700s are low impedance.
Even running my AD700s off a CMOY (TREAD powered with 470uF power caps, 1uF input caps, and 0.1uF decoupling caps - OPA2132PA opamp) makes me not want to listen to them UNamped. In my experience, all frequencies sound more clear and deliberate and the bass has much more presence. I don't believe this is placebo effect, as I have had several others make the comparison with my headphones also. Off 5 different sources, my AD700s just feel somewhat "weak" unamped.