I had decided to build an all-band low-pass filter to use with my propeller projects and others. In adding up the costs and spending a little time looking around, I decided to purchase a great little kit from Virgil Stamps K5OOR down in Texas rather than roll my own. His low pass filter kit fit the bill exactly.
I am working on interfacing it to the propeller and plan to do band switching automatically based on the frequency chosen. This board will easily handle up to 100 watts of power. You can see plots of the filter response here.