Congrats, I'm sure you will really enjoy the 100's.... they are beautiful sounding speakers.
When crossing over the mains to the sub, you should really let the Room decide which freq to crossover, and I would be sure not to cross over lower then 60hz, which will give the 100's a bit of room to still be effiecient down low. Too low and they start to lose control, so keep it tight. Do not feel that if you are crossing over at a higher Freq, that you are robbing the 100's.
By saying "let the room decide" I mean that you should be testing the freq response with a spl meter with a sweep of test tones and graphing the output, if you have a big dip in output where you are blending the mains to the sub, that may not be the best place to cross over. You want the graph to be as flat as possible where your crossing over, if its not flat your room may be presenting a problem to use that setting. Experiment with a number of different settings to make sure you choose the best for your room....
Again as Mazer stated, we would hope to hear a review of the comparison between the Aperion and the Paradigm if you could...
Go
here to download a test tone CD and read that page... As you can see in the graph on that page, they have a very nasty looking graph... What you are looking for is a nice smooth response much like this...
http://i34.photobucket.com/albums/d109/Warpdrv/HT-Great Room/HTPics014.jpg