Thank you for this thread. I just installed these today along with C5-570X coaxials in the rear doors, and the instructions here were quite helpful.
I did do a few things differently. I opted not to use the crossovers in the front, and re-used the factory tweeter wiring with the built-in bass blockers for the tweeters. For the rears, I did use the JL crossovers as there is only one line in from the amplifier for the factory coaxials. In comparing the overall sonic balance of those to the fronts, I don't think anything was given up (other than the switchable tweeter attenuation) by not using the crossovers for the component setup. Of course, if I were using an aftermarket amplifier, they would be a necessity.
Also, for the front tweeters I did not find the strap necessary. I filed the holes for a very snug fit, and there is no way they would ever fall out.
For some background, I am a pretty serious home audiophile and have some rather elaborate speaker and headphone setups, so I wasn't really expecting to be knocked off my feet with anything in the car audio realm. That said, for the price of the components I installed today, I was quite pleased with the results.
Overall, this was a worthwhile upgrade, even though I am using the factory amplifier. The C5s in the rear were probably overkill, but if I am going to go through the exercise of installing something like this, I may as well spring for the matching set to the fronts.
JL's tweeters really make the biggest difference here. The imaging on the front components is lightyears beyond the factory Sony's, which frankly at times you couldn't even tell if they were on. The detail and resolution on the C5s are excellent for a car speaker in this price range.
The one downside to these is that they further emphasize how pathetic the factory subwoofer is. Even with that placebo effect polyfill mod. Everything in the highs and mids sounds good, but the subwoofer is just belting out faint sonic queefs. I will need to consider some options to address that.
At some point, I plan on installing an appropriate aftermarket amplifier for the door speakers so they can really shine. Unfortunately, it is a little more of a task than I want to take on myself right now, and I'm not sure I trust the shops around here for that.