Quoted from Rdoyle1978:FWIW the Pinsound speakers (and specifically the woofer) sound -SIGNIFICANTLY- better than the FF woofer does. It’s just a way better driver, with a Kevlar cone and I imagine the PinWoofer driver is comparable. FF is good and a nice step up but it’s really important to have good drivers to go with the amp.
What? You realize the exact woofer being sold here can be bought for $22 shipped on Amazon right?
https://www.amazon.com/Pyle-Car-Subwoofer-Audio-Speaker/dp/B007JV7F4W
They are more than likely better than stock speakers but there is no way they are significantly better(or better at all IMO) than Flipper Fidelity speakers. 
And sorry for being "that guy", but the exact same amplifier and line converter can be had on Amazon for dirt cheap too.
Amplifier for $9 shipped...
https://www.amazon.com/TPA3116-Subwoofer-Amplifier-TPA3116D2-Amplifiers/dp/B07KNTZHCN/
Line converter for $7.99 shipped...
https://www.amazon.com/a12070600ux0556-Impedance-Converter-Adapter-Speaker/dp/B009T5S3HE/
Add another maybe $10 in wiring/hardware and you can get everything sold here minus the speaker adapter/ring for $50.
