Are you happy with the volume level you get out of these speakers? I always thought about getting rid of my premium system and just buying a set of two ways and run straight off H/U's amp, but I thought I would just get only fracture of what its capable of without an amp.
Let's see, these are 100w speakers, and the power your H/U can spit out seems to be 14w with 50w peak. Looks like you are missing out on half the show right there, but you said you want a natural sound.. Sometimes loud sound doesn't mean unnatural, but if the level of volume you are getting from the current setup, just get a subwoofer.
EDIT:
Found this, and thought it may help:
Written By Johnny Z said:
I have (4) of these speakers installed in my '04 Jeep Liberty. They are being pushed by a Rockford Fosgate Punch P450.4, and an Alpine CDA-9884 head unit. My concern was getting optimal performance out of a 6 3/4" speaker without having to use a sub (conserving cargo space). These speakers are amazing. Highs are sharp, mids are very tight, and bass response is unbelievable for a 6 3/4" speaker. If you get these speakers, make sure you have enough power to push them. Great product. I was always an Infinity fan (always bought Kappa and Reference) but consider me now a converted Alpine lover. These speakers pound. And GREAT customer service from Crutchfield. These were recommended by the tech advisor after letting them know what I was looking for. I only gave them a 4 rating because I don't give anything a 5. But these in my mind are definitely a 4.8. Can't go wrong with these speakers.