Replaced stock sub. Power loss?

I replaced the stock sub on my stock JBL system and I think the new Polk Audio 8" sub is pulling more wattage in turn lower SPL.(power) from HU or the other speakers.
Anyone else experience this?
My mind is made up now. Install a Alpine.

 

Are you using the stock amp that came with the JBL system? Are you sure you matched the ohm rating of the new sub to the old one you took out?

 

What you said doesn't make any sense. Unless the electronics in that JBL amp are even worse than I had imagined. But as said above, I would first try to match the impedance of the factory sub. Maybe try disconnecting the sub altogether to see if you get a noticeable difference in volume. Could it also be that the new sub is louder than the old one, making your door speakers seem quieter than before?