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Improvement when compared to what source? KZ EDC is not demanding to drive, I'd be surprised if you saw much difference using anything above one of the little apple lightning/usb-c dongles. Those dongles are actually quite good for IEMs, and beat many built in DAC/AMP units within phones.
You could look at something like the Qudelix 5k if you want more features (crossfade, eq, filters etc.) but that's out of your price range.
For a thumb drive DAC/AMP in such price category see availability of good old TempoTec Sonata HD Pro.
Regarding EQ and on Android see if your IEM's are supported by Wavelet.