Replaced the stock speakers in my 2018 4Runner Limited (w/ JBL) system. Here is what I installed and here are the results:
Front Dash: Hertz DCX 87.3 (3 1/2")
Front Door: Hertz Uno X 690 (6x9")*
Rear Door and Trunk Hatch: Hertz X 130 (5 1/4")
Subwoofer: Pioneer TS-SW2002D2 600W (8")
*Note: The front door 6x9" line feed is not full frequency (only bass), would probably recommend doing a 6 1/2" Hertz woofer instead as most all 6x9's are 2+ way, the Uno X 690 does crank out some nice bass though.
The Results: From audiophile perspective the sound is 5 times better quality. The loudness is about the same however, I can crank this thing to max volume and the sound is clear and really true for a stock head unit and amps. Very happy with my $500 estimated upgrade which I ordered from crutchfield. As a comparison it actually cranks harder than my Wife's Lexus GX460 base system.
The hertz speakers really run well with the stock setup and the Pioneer 2 ohm 2 channel sub cranks about 2x more bass than the stock sub.
Wish my system sounded this good from the factory. What have you done to your runner without breaking the bank?