I would agree w/ him for the most part… I also have the E17 and it seems to be adequate for amping the HE400s. However, something meatier w/ its own power supply (like my Schiit stack of Bifrost+Vali) should add some weight or power that the E17 just can't.
Furthermore, here are Lieven of Heafonia's comments re: amping:
Adding to this, I have only listened to my 400's w/ 2 amp's - the E17 & Vali. I much prefer the Vali which is a tube amp, and I think I have seen a lot of people recommend it to go w/ the HE 400, so you may want to consider it instead of Magni, UNLESS a smoother sound isn't what you're looking for.
I'm having serious problems with my HE-400s and I'm wondering if anybody has any advice!
Since I purchased mine about a year ago new from Moon Audio, they have never seemed loud/impactful enough. Using either straight from iPod/iPhone or through FiiO E17, the volume never seemed to get loud enough for me. The sound of the cans never got full and the bass has never felt impactful. Suspecting it might be the cable, I purchased a brand new one and still no change to the sound. I recently tried using them with a HP-P1, on the lowest gain setting, and when turned to a comfortable volume, the cans just sound horribly distorted, as if I've blown them out. Could I possibly have just blown them out or did I get a dud pair?
Is there anything I can do or am I just SOL?
Thanks in advance for your help!