Comparing the measurements of the old $400 version against the $250 SMSL SU-8, the SMSL is better.
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It’s using the current ESS 9038 (Q2M not Pro, that would be >$1500), so it can’t be that old. The chip was anounced the beginning of 2016.
Technically, you could run it directly to a power amp, as most don’t need more than 2Vrms to reach their full potential (this usually is in the specs for the product), but then you lose the features you mentioned.