Are you looking for a DAC? the DarkVoice is a tube amplifier with no DAC and the DX7s is a balanced DAC with built in amp.
If you're looking for a combo dac/amp, I would say get the new Topping DX3 Pro DAC/amp.
If you want to simultaneously run active speakers/headphones, particularly want a balanced setup, or a good performing DAC is your primary concern, then get the DX7s.
If you already have a DAC that performs how you would like, and...