I just replaced my factory JBL with RDS & without NAV this past weekend.
2003 Limited.
I replaced the stock subwoofer because the original JBL was totally blown. There was no rubber left on the surround of the cone. replaced it with a Kicker and used stock amp to power it. Plenty of tight sealed bass.
I'm planning a full write-up on my experience with this install, as soon as I get all the pics and info together.
I retained the stock speakers, JBL amplifier and all wiring.
I used a PAC TATO to integrate the new HU with the Stock JBL amp and a PAC SWI-RC to retain the steering wheel controls with the new HU, everything works great and sounds WAY, WAY better than stock. I think the JBL amp and speakers are higher quality that the average OEM speakers and the weak link in the JBL Synthesis chain is the stock head unit (HU). The stereo separation with my new system is incredible compared to stock.
I have a JVC KW-AV61BT
used a Scosche trim kit. I am ok with the fit. Yes the new HU does not match the dash lines exactly, but it is aesthetically appealing nonetheless.