Buzzing speakers

[Young Efficient]

Hi guys

So recently my brother drove my car for abit, and now the speakers click after a certain volume. I think the volume has been turned up way too much, I replaced the front speakers of my cinquecento, with some of similar age that worked great on my kitchen radio but crackle alike the newish 6x9s on the parcel shelf. Do we think this is the speakers, or head unit.

I am thinking of fitting some more speakers in my door pockets. So would it be an idea to get a new head unit and amp or would a simple head unit suffice?

Thanks in advance. Matt