If your amps have audible differences, then they will meet one of the qualifications[thus being easily measurable and coorelated with known human JNDs] as I stated in the last reply. It is irrelevant if your headphone amp costs $100 or $5000. Driving a headphone, linearly, is simple. When you start spending several hundreds of dollars for a headphone amplifier[that does not have an exclusive sound processing/effects ability], it would appear that more issues than just sound quality are a factor to the individual purchasing this product. I will not comment on this issue further, in the thread, in response to you, as it would be thread-jacking. If the original poster wants to go into this topic in the thread, then I will continue[with his authorization]. However, if this is a subject of interest to you, and you want to discuss it further, please open a new thread that is specifically targeted towards this subject and I will participate.
-Chris