SMSL DO400 measures fractionally better and drives demanding planars harder, but Topping DX5 II's LDAC Bluetooth input is a practical daily-use advantage most buyers will use more than the extra 0.5W of balanced output. For dynamic headphones under 300Ω, both units are effectively transparent — the DO400's Class A advantage is audible only on the most power-hungry planars. Pick DX5 II for featu...