Just got done installing a pair of JL Audio VR650-CXi in the rears. The sound is like day and night over the stock pair. Of course they're not drop in but it only took a couple of extra minutes to get them to work. Here were the extra steps that you'd need to do:
1) trim the opening to accept the larger diameter
2) make a spacer
3) remove some of the padding behind the speaker
I was able to install the driver side speaker without having to remove the seat. the passenger side had to be removed. Start to finish, including fabricating the speaker ring was about 1.5 hours.
Here are some pics of the finished product.
If anyone is interested in adding the same speakers in the back and you don't want to go through the hassle of making the speaker rings, PM me.