A direct bonded copper XP-G2 at 5.8 amps 875 lumens. This emitter is already near the peak output possible with a copper mcpcb and passive cooling. Lots of energy is turning into heat instead of light.
At 1.9 amps, a single XP-G2 puts out 460 lumens. Put three of those together, and it's so much more efficient that it puts out nearly 1500 lumens. Nearly twice as much energy is being converted into light instead of heat.