I don't use the LFE out, instead I have set the mains to large and no sub. In using the sub with mains approach, it allows me to set crossover freq down to around 50hz. I could also set different high pass and low pass freq in order to blend it better. In my base, 40hz high pass and 50hz low pass. Plus my center is also set to large and it crosses onto its own sub @ 155hz. I am still experimenting with high pass @ 131hz and low pass @ 155hz..
To do the above, you can't just use the crossover knob on the subs, but you will have to get a active crossover that has seperate high and low pass freq adjustments.