What car speakers should i get?

I have a 97 ford crown victoria and i just installed a 15 inch JL sub and 760 watt pioneer amp, it sounds great but when i get to real high volumes my speakers start to distort because they are stock. I want to replace the rear deck speakers so i can here the music over the subs. Can you reccomend some really nice speakers? i heard 6.5 and alot better than 6x9's. But i want to keep the price under $70 for the pair. got any suggestions?