Looking for a small increase in volume.

I have a 23 Tacoma w/ JBL upgrade (factory amp and sub as well). I replaced the stock speakers with 3 and 4 ohm speakers, as opposed to the 2 ohm stock speakers. There, expectedly, was a decrease in volume. I'm just looking to bring that volume back and wondering what the easiest way to do that would be. Any guidance would be appreciated!