I am not impressed with my Concept amp. It might push the rated power sometimes, but the power supply sucks. Really short weak signals will shut it down at times (quite often), but it can play most of the long excursions that should be much harder on it.
It is wired with much more than it needs (4AWG) and power to the amp never drops below 13.8V (even in long excursions), but it will shut off. I'm only running one RFZ12 at 4 ohms. The thing should take it fine, but... It is pathetic.
Last time I will be buying a Concept amp.