I went with Hertz after listening to JL Audio, Alpine, Focal, Dynaudio, MB Quarts, Eclipse, and a few other speakers I'm forgetting. I also listened to Hertz at 3 different Hertz dealers just to try and eliminate any bias from one or another dealer's set up. The Hertz had the cleanest, neutral mid-bass and the clearest highs without any listening fatigue from high volume for long durations. I threw in U2, Rush, Lady GaGa, and a few other CDs to hear the speakers under different conditions, and I literally stood there for close to an hour listening to these. I also closed my eyes and then signaled to them to switch speakers without telling me which... I always came back to the Hertz Hi Energy HSK 165s, even next to the $800 and $1100 Hertz speakers. It wasn't like Focals where I loved the $500, until I heard the $700, and then I loved the $700 until I heard the $1100. The HSK 165s sounded great.
Now, just to caveat this: The Milles did sound better with some source, but only On-Axis... Meaning, you had to be directly between the speakers, which doesn't happen in a car. No one listens with their head down by their center console. The other is that the XL sounds better with more power than I'm running. If you're running a clean 150 RMS per channel, than go with the Hertz Hi Energy HSK 165 XL... I'm not. I'm running 50-100 and the non-XL sounds great. The XLs handle more power, with the same sound quality... Which brings me to an important point: I built my system to be SQ (Sound Quality). It's not a system meant to just get loud.
The retail on HSK 165 is $499. You won't find it on E-bay for much lower except from Malaysia. I figured, I took up many hours of my local dealers time (not kidding, I did spend hours), and I appreciated the ability to hear these speakers side by side in a good atmosphere: I'll spend the coin. I did have one dealer offer me these for about $200 less, but again, I felt it wasn't right to not support my local dealer who was very patient and helpful. They knew I was only buying the speakers from them, and installing myself.
I initially ran these off the BA amp. It sounded a ton better than stock speakers, didn't really clip (I also had the center channel disconnected which helps a lot stock or upgraded speakers), and is worth your while. However, to really hear these speakers hit their stride, you'll need a good quality SP type amp.
These speakers are now powered by an "old school" Precision Power Industries (PPI) A (Art Series) 4200, which is 4 channels at 50 watts each. These amps are well known to be under rated. I did initially have it bridged to two channels, so they were getting 100 RMS each, until I realized it was mono. There really wasn't much sound difference, HOWEVER, I also have these crossed over really way too high. My "ear" says these are crossed over up above 500Hz (I bought a used Audio Control EQX and haven't popped the cover to see what it's dividing), and these are suggested by Hertz to go down to 250.
Here's the thread where I'm journaling my experiences... I need to update it.. I'll do it after lunch
http://www.camaro5.com/forums/showthread.php?t=152383