I put the same Infinity 6x9 in my back doors & was greatly impressed with the improvement. I didn't replace the front door speaker due to the crossover cutting off all the high frequencies & not allowing much gain. Put in a set of Polks in the dash. Overall very impressed with the upgrade. Got my Infinitys on ebay for $89 with free shipping.
i got the dash speakers installed and they are definitely brighter. The magnets are so much bigger and a quality construction. The 6x9 magnets are Huge!!! I am hoping good things as the Signal to noise on these is 91dbs so they should do more with the limited amp output. I am hoping I dont have fitment issues with the fronts. Now I just need to figure out how to install without the wife knowing!!
Well as an update, I pulled it off without detection!!! Gave up some motorcycle riding time by sitting in the Depot parking lot. I used the spacers that came with the speakers and except for some issues lining up the holes for the mounting screws and discounting the slight bulging in the door speaker grills from the tweeters they went in fine. Sound much better. I see what was said about the crossover cutting out the front door tweeter frequencies. I was trying to figure out what was wrong. Is there a way to disable the crossover? where is it located; a capacitor?
All in all, a very worthwhile upgrade for the price.