first off welcome to head-fi.
secondly, this is the "Dedicated Source Component" sub-thread/board, where people discuss "source components" ...i.e. soundcards, digital-to-analog converters, vinyl players, etc.
What you're referring to is the amplification process, and in that regard you should post your questions in the "Headphone Amps" board as the Mapletree amp you're referring to is indeed a dedicated headphone amp.
and lastly, to answer your question, if you stick around these forums long enough you'll understand that there isn't necessarily a hierarchy in terms of which amps are better than the other...it's about system synergy and about pairing the right amp with the right headphone (and possibly with the right source component should you want to further invest in this hobby).
Not all headphones are created equal, and as such they have different power requirements. The same can be said about amplifiers. So while the Mapletree may perform wonderfully with certain headphones, it might do worse with others. Thus I suggest you drop your notions of "headphone amp hierarchy" and focus more on the idea of system pairing and synergy according to your preferred sound signature and budget
That being said, Mapletree amps are known to be excellent with Grado headphones. You'll definitely get better responses if you repost in the correct forums
Hope this helps, cheers
Edited by Xan7hos - 4/5/11 at 10:27am