If you are going for very loud, as you say, I would recommed buying a stronger model like: https://www.kirstein.de/Live-Studio/PA-Systeme-Boxen/Partyboxen/McGrey-DJ-2222-Partykeller-DJ-Box-Paar-2-x-1000W.html - If you still want to be able to talk to each other these ones might just work fine.
For the amplifier you should go for something that meets the RMS power output of the speakers at the correct resistance. For example: 2 x 150 watts speakers at 8 ohms will do fine with an amplifier that does 300 watts per channel at 4 ohms. So the resistance is proportional to the power (unless you use anything other than 2 speakers). Higher resistance means lower power. Important: speaker resistance must not be lower than what the amplifier is able to do. So e.g. you can't use 2 ohm speakers at a 4 ohm amp.