Yeah that amp isn't that far over what you should feed an R but it's WAY too expensive. I have an 800 watt MTX amp that would power that R great and I only want 110$ shipped for it...You'd save 200$ right there...
There are alot of cheaper amps out there that will do the same thing...and as everyone said in your last thread, 700-800 watts would be optimal for an R.