I've only heard the AK380 SS once, and it was with its amp attached. It is a very solid-sounding combination, and comes really close to the SP1000 in sheer clarity and detail. In any case, the SE5-way Ultimate is a very revealing IEM that I've found easy to combine with various sources. Even though it's been over a year since I last heard the earphone, my lasting impression is one of amazement. Hence, it could very well be the IEM's innate strengths that helped you discern noticeable differences between both states (with and without the amp).