Bose or base stereo? Components sets where the 6x9 plays the low end in the door and the tweeter/wideband plays the higher frequencies are somewhat mated. to one another Specifically, the crossover between them and the sensitivity is really important, since you can't adjust any of that stuff with a stock head unit. I would replace the doors and the dash speakers together with a crossover. 4-ohm will be OK, maybe a tiny bit quieter. This Onehttps://www.sonicelectronix.com/item-18 ... SS269.html
is probably good.
If you really want 2 or 3 ohm to just replace the door woofer, Infinity, JBL, and CDT make them.