That is probably a good amp, no way of knowing without testing it first though. Harman Kardon, Bose etc do make good stuff but most of the time the installs they put in cars as an option (BMW/Audi/RR etc) aren't great because the car manufacturers give them a stupidly small budget so they can make a bigger profit, people still pay for them though because it has a well know audio brands name on it. Win win for the companies, not so good for the customers....better off spending the same cash or less on an install from a good car audio shop.
So just because they're in BMW's doesn't mean the quality is upto that of a home stereo system from the same manufacturer. It's the same old story, you can't buy something because of the brand, you have to test the specific model.