What did these sound like without amping them? And did you install the crossovers?
You will notice some difference just by changing the standard renault ones to some aftermarket ones without amping. I did anyway when I just swapped the standard renault door speakers for some Sony coaxials. Well they went to a higher volume before distorting anyway.
I didn't try my components unamped obviously, but when I upgraded again to the amped components the difference was impressive, much better sound quality at all volumes really.
You can find 2 channel amps on ebay for silly money. Its just laying all the replacement wiring that was the hardest, but there are easier ways of doing it than I did probably.
Yes I installed the crossovers, Just velcroed mine under my seats. There's not much point buying components if you don't use the crossovers! They are the things that filter the sounds, so only the high frequency goes to the tweeters, and the normal/lower frequencies go to the door speakers.