It is possible to get near that number is what I would say if you are running on a high amperage and you are using a very good lens like the g-1 or something. 1.62A atleast, but it would be near 1.8A if you want it that power. And your diode has to be a high effiency one.
All I have got is 2.15W (running at 1.62A + g2 lens) but that wasn't my build.. I bought it off someone.