You can see from my signature that I installed JL Audio C2-570X's. As you stated, I just replaced the front speakers and the difference in clarity and SMOOTH high end is night and day. IMO, JL Audio owns in the "affordable" aftermarket speaker world. However, I'm sure you'll hear a lot of opinions and biases that may make your discussion that much more difficult! I can definitely say that if you go the JL route, you will not be disappointed. Check out Amazon.com - they can be had for ~$100/pair.