Frequency response and crossover
Blksnday,
You are confusing a couple of the frequency specs on your speaker. These specs refer to the internal crossover in your 2 or 3 way speakers:
Fronts L & R: cross over @ 150Hz, 4KHz
Surrounds L & R: cross over @ 4kHz
Center: cross over 400Hz, 4kHz
For example, the fronts have a woofer, mid, and tweeter crossed over at the frequencies indicated above. Don't worry about these specs. However, you need to look up the frequency response of the speakers which indicates the range of frequencies they can produce. It should be something like this:
60 Hz to 20K Hz +/- 3dB
The sub crossover must be high enough that there is not a gap between the frequencies that the sub can produce and what the speakers can produce. Your surrounds will probably cut out at a higher frequency than the mains (80-100 Hz) so start with this crossover setting.
Set this crossover setting on your receiver and use the LFE cable to the sub. No turn the crossover knob on the sub all the way up to 150 Hz so it doesn't interfere with the receiver.