Have you checked out the direct fit pioneer speakers? In all honesty the speakers in the Clio are too small for me but I've got them and while at first they're a bit harsh give them a bit of time to bed and and they seem quite good now.
They're great speakers but your Sony headunit outputs around 16-18W RMS. It may struggle to power these if they are close to the quoted 80W RMS. I found that adding soundproofing behind the rear speakers makes a very noticeable difference