something like this would be helpful to you only in your garage
if you wanted to hook the power supply up to your amps / batterys to play the car with the engine not running.
like if you were building a pure spl viechle and did daily testing with a term lab to absolutely fine tune your car to get the max score by every little bit.....
otherwize - you could bench test high power amps with the power supply - or rig up one hell of a home stereo system using big or a bunch of car amps with it.
totaly not worth 5 grand