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The L30 is good, but the L30 II is kingpin for IEMs if you ever go to them. The noise floor on both are really silent, so I'd get either of them over the Zen.
You can use the iFi's Xbass feature to correct the HE400se's deficient bass response.
In a system where software EQ isn't possible, that feature alone will most likely result in better sound quality.
However, if you're able and willing to apply software EQ via Equalizer APO, SoundSource etc, then the HE400se's frequency response can be corrected much more accurately and Xbass loses its value.