Best CHEAP 6.5" car speakers?

I recently bought a super cheap car, and my goal is to keep it that way. I bought a super cheap head unit for it, and am wanting to know what the community's thoughts are on the best super cheap speakers would be for it on Amazon? I've always had nice systems in my cars with amps for all of the components, but I wanted to have try a different route this time. Are there any surprisingly good (for their price) speakers that are sub $40 on Amazon that you have had experience with? The front speakers I am replacing are 6.5" and they need to be fairly shallow from what I can tell. The music primarily playing through the system will be Japanese pop from the 1980s.