Sorry I can't give a proper review as I am yet to receive the product. The delivery team is being totally uncooperative. I'm starting to regret paying for the product in advance.
When buying a pair of HE400SE from Gears For Ears, I was recommended to get a pair of DAC/AMP to fully bring out the potential of my planar headphones. Having tried playing the HE400SE through both my motherboard's "premium" DAC and the FiiO E10K dac/amp, the difference is immediate.
If you are planning to get into the audiophile hobby but are not sure what dac/amp to buy, then this is a great entry point as the E10K is priced quite aggressively given its features.