I recently used Rockford Fosgate's punch level coaxial speakers (the P1462 and P152) powered by the ASA 400.4 amplifier from Powerbass for a family members 01 Jeep Wrangler. With Rockford 4x6's in the dash and Rockford punch 5.25's in the sound bar I was able to get an extremely punchy sound with a good amount of lows mixed in that sounds amazing at high volumes. It is a great set up for people looking to keep their audio system at a reasonable budget but still hear their music loud and clear whether on the highway at 70 mph or in the woods for some weekend fun. The job should take someone with minimal car audio knowledge about 4 hours, but either pay someone to do it or take your time if you have no experience because this combination fits the wrangler perfectly and looks great it done right.
I should also mention that the Rockford speakers sound great without the amplifier which will save you about $200 but still expect volume to be compromised by wind noise at faster speeds.
As for a radio, she already had a pioneer radio installed in the car, but I would suggest anything from pioneer, Sony, JVC, that have aux in and USB capabilities. USB allows for music on flash drives that will never skip like CDs. Expect to pay 150-200 for it.

Email me for pictures nate4164@gmail.com

 

An external amp is a must. Get an used Eclipse 5 channel amp from E-Bay, two new 5 1/4 component speakers for you sound bar, and two new front panel speakers. I recommend Infinity for price and sound quality. Amazon will have the best price. Get a single 10" woofer from Craig's List for around $75 and your Jeep will sound amazing.

Maybe even like mine : )

Oh yeah, you cannot fit an amp under the rear seat, it has to go in the back area.

 

Pioneer DEH44HD was not in the list... pretty good unit

 

Had to make my own cherry burel dash adapter to mount the stereo also had to weld up the galvanized mount tray to fit the Cherokee dash (seems no one sticks adapters for XJs anymore) also salvaged the female plug from the original radio to preserve the xj's wiring harness.