There is no "cutoff" at the crossover frequency as sweetspot mentions, there is a natural slope or hand off to the sub. The sub, which "moves" more air than 2 6.5" woofers, does a much better job with this "burden" mentioned. Even at a 60-80hz crossover and set to small, the 60's and 80's will still be putting out potent bass. Small has nothing to do with the physical size of the speakers, it has to do more with having a sub in the mix and the speakers ability to play below the crossover point designated.
Here is a fine blog article by Dr Kriakakis which discusses concepts even Dr Holman (founder of THX) has discussed for decades.
http://www.audyssey.com/blog/2009/05/small-vs-large/
