Compact builds need parts that fit, not parts that merely work. The ASUS Dual 5070 is the right GPU here: 2.5-slot, dual-fan, sized for SFF cases instead of stretched to fill a triple-fan shroud. The Lian Li A3-mATX is a 26-litre DAN Cases-designed chassis that takes a 360 mm radiator if you want it; the NH-D15 fits underneath at 165 mm.