Well if you only have 400rms then the P2 is the better choice but I would still suggest the Audioque SDC2.5 or even the basic SD2 over the Rockford P2. Now on the other hand if you have a good 1500-2000rms then get the HDC3 12 but judging by you wanting to comapre it to the Rockford I doubt you have anywhere near that kind of power.