35 might be better than 25, but still much worse than dx240. This is speculation since it did not heard 35. Dx240 is indeed outdated, but it works pretty good. Don't support system wide PEQ due to outdated Android.
I'm no longer using dx240 because bought Fiio M17.
Dx240 one or two steps higher in sound quality. I own it and heard sr15-sr25
My bad for 3dB thing. I think current is consequence of voltage and if output impedance of amplifier is low, current is unaffected. If output impedance is comparable with load impedance, voltage and current arrived at load is reduced.
Thank you for spec for HE6. On paper it should be plenty loud at 4 V
4 volts RMS would be enough for 99% of headphone market, and this voltage is industry standard. If output impedance is low, it will be able to drive low impedance headphones.
For stuff people mention,like HE-6 might need more, I don't have much experience. You can calculate loudness of headphone based on dB/V spec. Every doubling of voltage increases loudness by 3 dB
But if amp make any your headphone better, you basically improve anything in your collection. And you also don't change headphone. You end up with, let's say HD600, but better than other HD600.
After all, Audiophilia is about small changes meaning much for a person
I use DAP, so change both DAC and Amp. Fiio M17 is divine and way beyond anything cheaper I have
Yes there are diminishing returns. But sometimes people feel that 5-10% performance worth 2x increase In price.
Also everyone point of satisfaction is different, because garbage 3 dollar earphone is much higher price to performance ratio than 20 dollar IEM gem like TE Zero.
Someone does not want to spend more than $20 because diminishing returns, some one spends no more than $300 because diminishing returns. Someone spends $4000 because fuck it.