Hoping to revive this thread as I also have an '07 FJC with the system which includes the sub. (Not going to the garage now, but pretty sure mine includes an amp under the passenger seat.)
First, a little background. I am so happy with my FJC. Bought this cherry manual 6 speed when I worked in the oilfield in ND for 8 mo in 2014. Currently 190k miles, and knock on wood, the most amazing vehicle ever. I have done minimal mods:
-added air horns wired to the steering wheel, and added a switch in one of the available slots to keep the OG horn for "light work". LOL
-added a Bluetooth backup cam, mounted into the bumper between the spare and hitch (has its own screen I chose to Velcro in the empty space to the left of the steering column)
-added this Bluetooth unit for connecting my phone to the stereo:
https/www.amazon.com/dp/B009NLTW60?ref=ppx_pop_mob_ap_share
(since my Jammer 6CD changer died like everyone else's, I have a magnet mount for my Pixel phone plugged into the CD slot and use my phone nav and music...this Bluetooth unit gave my whole stereo new life!!!! But I want a little more...)
Now, based on this and the seemingly infinite other stereo threads I have been researching, I purchased the replacement sub yesterday from this thread's OP.
I plan to upgrade the front door 6x9s also, and likely the dash speakers per Zoso's suggestions. However, I haven't decided on upgrading the HU. I have been heavily considering it, but from the minimal mods mentioned above, you can see I don't need or care about SiriusXM or in-HU-nav or Bluetooth calling or in-HU-backup cam, as I basically have all that covered. (I don't care about wires, I keep things clean enough.) Also, I don't really use any steering buttons other than volume occasionally. (My FJC only has the buttons on the left side.)
Bottom line, do I need to purchase a new HU for this new sub and the other new speakers I would purchase? A few of the threads talking about losing some of the whole system "pre-programming" makes me hesitate. (Don't want to go thru the efforts to install a HU and have everything sound worse. I would definitely do it myself, BTW.)
But maybe I need some more power? If I do get another HU, that would likely be the only reason...if the speakers need the power boost. Likely would get the simplest Kenwood, etc. that would serve that purpose.
Please advise, and thanks in advance!