Keep in mind that's the one designed to run at .5 ohm. regardless of if it's the .5, the 1, or the 2 though, they all run in the high 80's for efficiency at maximum output. 87% IIRC. Plus, Hand assembled in the USA, top notch components, and tiny footprint.
Also, look on eBay if you're open to used. They have various models that put out 1500-1800w as well. And you could get one of those for $300 or less probably.