us amps aren't in-effiecient. their huge class AB's is what gave them the rep for drawing a lot of current. with any huge class AB, ...... if you're not drawing big power, you're not making big power. like their old usa 6000 (6000 watts) took about 900 amps or so at full tilt. their class D's are very efficient and their class AB's are just as efficient as the rest in the industry.
like audiolife's comment about a 2kw claim and the amp only draws 50 amps. if the amp is drawing 50 amps, it sure in the heck isn't getting any where near 2kw.
there's lot's of decent amps out there. lunar and DD amps are a couple that pack some power in a small foot print.