I would use a REL or similar and cross them as low as possible. A friend of mine is trying out one I bought recently with Quad 57s. He has gradually lowered the crossover point to 25Hz, which is the point I use with my two RELs with Spendor SP1s. I run my main speakers full range as I can hear a degradation when running through the crossover, I think you would be able to hear it through the Maggies also. But you can try it both ways and see for yourself. I would not run them above 30 Hz but again you can try it yourself. The RELs run off the amplifier power output as well as line level, this is the method I have described. If you do not have an output that is controlled by the amps volume control it is hard to use line level output to drive the subs.
