1. The cheapest that comes to mind is the Topping DX3 pro for a bit over 200$. It also has a headphone amp that will probably make the Atom superfluous.
2. Buying noname / cheap is a false economy, when resale is taken into account you end up spending more money in the end. There are cheaper options but nothing I'd want to keep in the long run. The Saga has a stepped attenuator, a passive mode, 5 inputs and two outputs. And the tube buffer. Buy used if you want to keep it under 300$.