I've been debating all night on which subwoofer to order and i think i'm going to with an Alpine Type-R SWR-1042D which runs at 500 watts rms at 4 ohms, if i use a Sony XM-2200GTX amp which is a 2 channel amp and bridge it to 500 watts rms will i lose power i've heard having a 4 ohm sub cuts the watts you get from your amp in half is that true?