Personally with a 10x4, I'd keep a gatf, albino silver aro, a few nice stingrays, Tigrinis, and perhaps aimara. Big docile dithers are important such as the albino silver or even tarpon. I also like some nice peacock bass but depends if the tank is getting too crowded. In Asia, for sure id throw in a main red or blue base gold arowana as well. My current diplogramma channa is almost 16-17" and is transitioning to full blue and has been very comm friendly as well. In such a tank, I would absolutely avoid dorado in my own past experience. My old dorado would cause ridiculous havoc with everyone. I've never kept a lunch before so I wouldn't know how it affects the tank dynamics.