Front speakers

99 passat 1.8t. I need to replace front speaker(s) and i noticed that it has 4 wires coming in (also I noticed that it is riveted--crazy). Will any speaker will go in there, or I have to do some readjustments. I like the sound in my car and I would like to keep it as much as it is as possible. I don't want to drill out rivets just yet before I get more info. If anyone can advise:

- what kind of speakers can I use?
- and why are there 4 wires (again please)?

You have to drill out the old speaker. I would reccomend stock speakers unless you have a aftermarket deck.

the wires are- ground-signal-power-power not in that order but thats what they are for