I was advised to purchase these speakers by a friend in the know about 'pimping' stereos. I bought them and changed them with the factory standard speakers in my Vauxhall and the difference is extremely clear.
The sound is now deeper, you can hear so many different levels in the music due to the fact that they have the integral tweeters (my old ones were mid range only). It is also crystal clear with very little distortion.
Not only this, but they look amazing installed in the vehicle, and there is the option of leaving the front covers off if you need to install them under a door pocket.
I will never go back to anything other than Infinitys now - they are excellent value for money and really deliver on quality as well. I have since hooked them up to a Kenwood Amp and the sound quality has got even better, and they fit really well into the rest of the rig.
A big thumbs up from me.