Have you tried the high-powered Alpine series? Go to crutchfield.com to search and read the reviews. If you don't mind me asking, why do you want so much power? 300 to 400 will run me out of my car. LOL
well, thats kind of an open ended question....., you can do 2500rms@1ohm, or you can do a pair of 1k-1200rms@2ohms. just have to know the amp dyno/birthsheet results. theres a lot of amos that run much more efficiently at 2 ohms, which you can tell by the rms output at each ohm load. unless its an auto sense amp, it would be something like 400@4/800@2/1k@1. that right there tells you that at 1ohm, it will drag the power supply down so far that it cannot maintain full rail voltage at 1ohm, full power. sure, its made to not blow up, but it will also start hogging more current than it should need. it would be easy to just say, like sundown 2500, but lets start with a little more info: what vehicle, alternator size, wiring size (big3?) and options you are looking at, including budget. you may simply not be able to support over 1200rms, and would be wasting effort in the wrong area. rule of thumb is 10w per amp of alternator power or less, so you would want a 250a-300a+ alternator and supporting wiring, plus a battery/cap setup suited for ac ripple dampening and possible high charge/discharge rate..... you may eat your budget up just in supporting the power/ground cable requirements.... i would start with your goals, which we outlined, then the required wiring (dont forget that connections and blocks can eat a good bit of the buget, too), then make sure the battery isnt going to get cooked, then upgrade the alternator, then, finally, once its all up to par, put the beans to it. if you find something thats 2500rms @1ohm, and 1k-1200rms@4 ohms, or even down to 7-800@4, then you could buy it now, run the subs series-parralell to 4 ohms, by running coil a of each in seris, coil b of each in series, then paralleling those back to 4. then, once you can support it, parallel them all to get to 1. you can still get a lot of decent output at the 600-800 level, and many amps are seriously underrated, or overrated.