How do I know what kind of amp I need for my speakers and sub?

The first person is wrong about your sub, it is rated at 500 Watts RMS, which means your amp should be at least 500 watts RMS as well. As far as your other speakers I would hook them up to the sony head unit without any further amps, you only have the 1 sub so you don't need amps for your highs. So here's the bottom line, this is what you want: Mono amplifier rated at 500 Watts RMS AT LEAST (it's okay if the amp is a LITTLE more) don't pay attention to peak ratings they are deceptie, RMS is the level that they can operate at all the time, Peak is the rating they can only sustain for a brief second, like a hard b line. RMS is a much more reliable rating. I would also suggest you buy a 1 farad capacitor for your amplifier(it's like a little power cell to keep the amp running at optimal level that connects between the amp and the battery). I hope this helps good luck.