There are a few web sites for you. You should be able to find all the answers you need on one or all of those sites.
When choosing products I like to choose the sub first. Reason being is the sub is going to occupy the most space in your car so you have to be certain it will fit. There is no point in buying a 1000 watt amp when you only have room for a single 8". So determine how much airspace you are able to sacrifice then you can decide which sub(s) can fit in that area. Once you know the speaker specifics you can pick an amp that will work well with the drivers.