When I look at the reviews of speaker replacements at crutchfield they are all mixed. they all have some complaint about bass response not being enough but also praise about it being good. I wish there was a way to sample them instead of buying blind. I realize that others are buying for different cars, but not sure why such a disparity in opinions. Has anyone replaced the 4 speakers been satisfied without adding a sub?
I investigated this approach and decided it wasn't worth it. I measured the stock speakers as amazingly flat down to 50 Hz with usable extension down to 40 Hz. Short of a much larger speaker in a large enclosure it would be difficult to do better than that.
Note, I'm talking about frequency response at moderate SPL only.