In my younger days, I didn't think a stereo had any bass unless it had 2 or more 12's, but I've grown up a bit. I still think a quality stereo needs a sub, but a nicely powered single sub will fit the bill. I had a single Elemental Designs 12 that was getting 375 watts in my last install and it was enough to be completely over-bearing. A single 8, 10 or 12 will do the job but I don't think a stereo is complete without a sub of some sort.
2013 Race Red GT/CS 6MT; Elec Pkg; RAAMat on the doors; Morel Tempo 5x7 coaxials; GT500 axle-backs painted black