How do you high pass your main speakers?

I have been very happy with the distributed bass array I added to my system, but from what I hear, the optimum method of integration is to high pass the main speakers.

Two questions:

1. What are my options for accomplishing this? Does this need to be a feature built into my amplifier or is there another component that needs to be inserted in the chain. 

2. What crossover point would be ideal? What frequency and amount of rolloff would be best if my speakers are ATC SCM19's which have a frequency response of (-6dB) 54Hz-22kHz.

Cheers,

Tony