Sometimes the best equipment is your ears
Use the supplied test CD or music of your choice to adjust the system. The manual give steps to do this, the closer you follow the steps, the better the results. I'd probably start with both filters on the sub set around 45Hz. Then, I'd adjust the phase for maximum output around this frequency. Adjust the sub volume so it seems the same as your Silverlines. Adjust the crossover freq up or down to get the best match. Sit back and enjoy some music. Listen for a few days and then maybe you'll have ideas of some additional tweaking. (all this is assuming the sub is broken in)
As far as hum, sounds like potential cabling issues? You shouldn't have any hum from your main speakers, that shouldn't have anytying to do with the sub.
Check the Subwoofer setup tips and tricks thread as well