i used some 6x8(5x7) speaker adapters to fit some 5" component speakers. Couldn't be happier. I did this in front and back and used some denon components. I am just using the stocker head, and using an amp will definately make them sound better. If you have the audiophile system with the sub, then i recommend using an amp at least for the rear speakers because they are a lot softer than the front for whatever speakers you use. The problem with ANY head amp, it is not as controlled as an external amp. This is probably why you encountered distortion. If you use some kind of external amp, I used a low end alpine in my escort when i had it, mrp-f200 and it sounded great, no distortion. It is rated at 25 watts rms x4. i am sure you can find one of those for pretty cheap. Mine came from ebay for about $25. Point is, if you use a high end speaker on the head amp, then you are wasting money because you will only get distortion at upward volume. If you use an external amp, then it will make most speakers sound much better.