I'm at least glad to see that people are passionate about giving "good" advice. I think everyone is a little right and wrong in their answers here, as we're all seeing "good bass" as a totally different viewpoint. It's true, sometimes, the number of subs will not make a difference, but sensitivity does make a difference, but so does the box size, make and many other characteristics of the amp. I would like to note that just because someone is hitting over 160 db with two subs, doesn't particularly mean it's good bass. It just means it might be hitting 160 db at a certain frequency and not over a spectrum. What good is that? It's all up to the listener, so if they never play music with sounds below 40 hz, then they can choose accordingly. There used to be some guy on this board who kept saying he knew a lot about car audio and bass because he had three noise pollution tickets to his name. That doesn't mean anything, since we've all heard that one clown around town that has the absolute worst distorting system in the world with all his windows rolled down thinking he's attracting the ladies.
None of us will ever know each other's listening tastes, and to tell you the truth, my right ear is damaged, so I may never know what great sound is like anymore, but I do know enough of the theory to know that a sub that big peaks and dips at certain frequencies makes it an unreliable sub with big sound holes.
If I may also interject a lot of people in car audio disliked the certain audio scoring methods, because they used a computer to monitor perfect flat response lines, which are actually not in tandem with our "reality", since the human ear responds differently to different notes. So even as humans, we are perceiving sound differently from the computer, and the flat line is not the same thing we actually hear.
Think of it this way, at least we're all trying to keep him from buying the Kicker Squares, and saving some cash is the least anyone can do. Also, unless you're in a stretch limo, Suburban or Excursion, should you really worry about how hard a sub hits past 1 or 2 meters?