One other thing to watch out for when picking an amp is what voltage they are rated at. what you are intrested in is what the watts are around 12 volts. If they say the amp is 600 watts at 12.5 volts then you will get 600 watts out of it. If they say the amp is 600 watts at 14.5 volts your not getting a 600 watt amp because the amp will more than likely never see 14.5 volts. The rating at 12.5 could be 400 watts. JLaudio has amps that have the same output from 11-14.5 volts and also the sub can be 1.5-4 ohms.here is an example of the 500/1. Rated Power: 500 W RMS @ 1.5 ohm - 4 ohm (11V-14.5V) . I would use jlaudio for the sub and amp. I use the old US amps. The new amps have changed and I do not know if they have changed the internals or not. The old style amps kicked ***. You can still find them on ebay. shawn