JBL Speaker Only Upgrade Install/Write-up

[Mem4runner]

And to answer my own original question, the new 3.5” dash speakers are plenty bright on the high frequency tunes. There is absolutely no need to also install tweeters with the 6x9s in the front doors

 

[Jrunr]

Is there an actual "drop in" subwoofer that we can use to replace and improve on the factory JBL subwoofer WITHOUT adding an additional sub amplifier?

I have found a couple of DVC 2-Ohm subs on Crutchfield, but I don't know if just putting one of those in the factory enclosure would increase bass output or not.

The only one that seems to be efficient enough and able to dig down into the 30hz range is: Audiofrog GS8ND2 GS Series 8" subwoofer/mid-bass speaker with dual 2-ohm voice coils at Crutchfield

But I have never heard of this brand before, or know if it is a credible option...

The other 3 options I found were:
1. Kicker Kicker 48CWRT82 CompRT Series shallow-mount 8" subwoofer with dual 2-ohm voice coils at Crutchfield
2. Rockford Fosgate Rockford Fosgate P3SD2-8 Punch Stage 3 shallow 8" subwoofer with dual 2-ohm voice coils at Crutchfield
3. Pioneer Pioneer TS-A2000LD2 Shallow-mount 8" subwoofer with dual 2-ohm voice coils at Crutchfield

Do you think any of these would be good options for a drop-in replacement to get more bass?