I replaced the factory speakers in my Supra (which were fairly good by factory standards) with Diamond M5's. I didn't want to have to rework my doors too much, so I needed 4" drivers (the same as the factory speakers) - so it's a good head-to-head comparison.

In fact absolutely no comparison can be made between the factorys and Diamonds - the sound quality with the new drivers is incredible considering their size. The clarity is beyond reproach and the volume of sound you get from such small drivers is hard to comprehend - you would think there were 6" drivers fitted if you didn't know better.

So, I would suggest that replacing the factory speakers can in fact make all the difference in the world, as long as you go for a good set of components (and include that sub as well of course).

Rob