Hey, sirhk100
dB vs. Feel of the hit would normally go hand-in-hand. The bass that you "feel" is normally between about 15Hz (most systems can't really do that, btw) and about 150Hz. When you are doing SPL competition, you just try to get as many dBs as possible. The way to do that is lots of subwoofers, lots of power, and a bass-test disk at around 40-80Hz (that can change, depending on the system). So, I guess to sum it up, the dB is a measurement of how much air you can move.
Hopefully I answered your question (at least a little bit). If not, we can get a whole lot more scientific about it *grin*. I used to do SPL competitions about 3 years ago, when 140dBs was a LOT, and 150dBs was just a dream.... It's scary to think that most SPL vehicles out there these days can blow that away. Oh, well...that's to be expected!