I have a laredo with the standard sound system. Here's what I replaced it with
Pioneer Premier DEH-P3900MP (deck)
Boston Acoustics Pro 60 (front component speakers)
Boston Acoustics SR65 (rear speakers)
JL Audio 10" 3w3 (sub)
Alpine MRP-F450 (4 channel amp for speakers)
Alping MRP-M500 (mono amp for sub)
First impressions, everything sounds amazing. The acoustics of the Grand Cherokee are better than any vehicles I've owned previously. I can crank the volume up louder than I can stand it and if I get out and close the doors, you can't hear or feel much from outside the vehicle. (So you won't be 'that guy' rolling down the street breaking windows). Inside the vehicle though, everything is loud and the bass kicks hard.
I normally put amps under the driver and passenger seats but because of the battery location and the false floor under the seats I didn't want to put them there. There wasn't enough room under the back seats and I didn't want to lose any cargo space so I stuck them on the rear of the back seats. I think it looks pretty sweet and it saves space.
The sub box is heavy enough that it didn't need to be mounted down. If I was gonna do any serious off roading though I'd probably want to secure it somehow or take it out for the ride (takes 5 seconds to remove from the vehicle.)
I threw a picture of the tweeter in too because different from other vehicles I've owned, the grill on the factory tweeter is part of the tweeter itself rather than the tweeter enclosure so you won't keep the factory look if you replace the tweeters (I think this way looks cooler though).
The other great thing about the WK2 was the battery placement under the seat. It made the amp install much easier than normal.
If anyone is considering redoing their audio setup I highly recommend the equipment I chose. If you're into rap you may want a bigger amp or a bigger sub, but this one can kick harder than I'd ever want it to. In fact, I've got the low pass filter set around 75hz so the bass is really clean and tight (no shaking the car next to you).