Speaker - Non JBL in place of JBL

That is not advisable. Here's why;
Your factory system uses:

2-ohm speakers (low Impedance)
This is NOT a standard setup

If you install normal speakers (4-ohm)

1. You'll get Lower volume
Amp sends same voltage

• Higher resistance (4Ω vs 2Ω) = less power
• Noticeably quieter system
• Weaker bass

2. Thin / weak sound

• JBL amp is tuned for 2-ohm load
• 4-ohm speakers won’t “wake it up” properly

• You will NOT damage the amp
• Running higher resistance is safe

In case you're wondering why Toyota did this?

• Gets more power from a small amp
• Improves efficiency

So my friend, you are stuck with either shopping for 2 ohm speakers, or begin saving for a full upgrade of amp and speakers to a more readily available 4-ohm set up.