Well I was wrong... the factory speakers are not 6dB louder than the Infinity speakers... just to get that out of the way. But they are between 3-4dB louder.
Did some testing today.... measured each of the speakers listed below with each one mounted in the left front dash. The SPL meter tip was 1 inch above center of speaker (although moving it around a 1/2" or so did not change the level). I recorded a 1kHz tone from REW... and also Pink Periodic Noise full range (FR) 20Hz-20kHz. I also measured the resistance of each speaker.
Factory Speaker
4.1 ohm
1kHz = 85dB
FR = 84dB
Infinity Reference 3032
2.6 ohm
1kHz = 81dB
FR = 81dB
FaitalPRO 3FE22
3.9 ohm
1kHz = 85dB
FR = 84dB
I already had all three Infinity speakers in the dash and they have been very disappointing to say the least. They are clean, but the highs are rolled off, and/or they don't have very good off-axis response, despite bouncing off the windshield. I installed one of the FaitalPRO speakers in the left side and left the Infinity on the right. I played several songs with the bass EQ slider down at -9 and faded fully front, then quickly moved the balance slider from left to right and back to left, so that I could compare the two speakers. The FaitalPRO speaker was no doubt better sounding to me, and the highs were back. The Infinity sounded muffled (and I tried more than one... as I had one pair from Crutchfield and one pair from eBay). I then decided to try the factory speaker again... and it was still a wee bit brighter than the FaitalPRO, but it was very close in the highs, although not as harsh as the factory speaker. I could tell I was not losing any volume with the FaitalPRO like I was with the Infinity. The real difference came when I cranked up the volume to 30-32 and moved the balance control back and forth. The factory speaker sounded very distorted on several songs, while the FaitalPRO was very clean (as was the Infinity). Clearly the factory speaker is inferior when it comes to power handling and high-volume sound. Surprisingly on some songs, it held its own, but you could tell when it was not liking a particular song. So the Infinity and FaitalPRO are clean, but the FaitalPRO has more volume, and it matches up better with the remainder of the factory system better in my opinion, although I still want to replace the upper door speakers... and rear headliner speakers with the FaitalPRO.
I need no further testing and or convincing that the FaitalPRO are the clear winner for me. I installed all three across the dash and now this system is literally amazing, even without a subwoofer. I can now crank the bass EQ back up to around +4 with the mid at +2 and the high at +5. The front stage is seriously good. Again, not competition sound quality grade, but still very very good for a factory amp powered system. I have ordered 4 more of the FaitalPRO speakers to install in the top of the door and the rear headliner. The only drawback to the FaitalPRO is I had to dremel off one of the four tabs and create my own holes with screws in the mounting area, which was not a big deal, but they are not just a drop in using the same screw holes.
Keep in mind, this is all my subjective opinion as far as what I like in my truck. I am not judging anyone else that has these Infinity speakers... they may be exactly what you want and/or may sound different in your truck. I am in NO WAY suggesting you have inferior speakers in your truck. If they are working for you, they may work for many others as well. My point being... try whatever you want to try and keep it if you like it. If you haven't been happy, you might consider other speakers.... and the FaitalPRO may not be what you like. I just happen to love how they sound in my truck.