Do you need to amp them? No, you dont NEED to amp any speaker. Speakers can be powered from the head unit. HUs put out about 18 RMS and those speakers can handle 40 RMS. So, if you WANT to amp them you can, safely up to 40 RMS.
If you want decent volume levels with good bass-midrange response. You should definitely put a amp on them. Without one the sound will be very "thin". This pretty much goes for any aftermarket speaker. I would recommend a amp that does double the RMS rating for best sound.