Even if you stuck Pioneer TS-A6972R 6x9's in there, they are going to sound much better than the joke "Infinity Premium" system that comes stock.
According to the TS-A6972R's specs they go down to 28Hz for some good bass. Not very many 6x9's go that low. The stock bass-reflex housing that mounts the speakers are not exactly rocket science, but a better speaker mounted in there sounds wonderful.
Subwoofer? Stick the Logitech Z-2300 in there
I'm not a "boom boom" guy either, when I like to play jazz, I want to hear that deep, rich string bass. When I want to hear rock, I want to hear that tight drum set and bass and I want to hear it cleanly. 40Hz bass buzz and boom is not the highlight of my music but I can hear it cleanly since ripping out that stock "Infinity Premium" crap that came with the car. I have yet to stick a subwoofer in my car because the space and tuning is just a complete nightmare.