I've always been pleased at how well 4-pole filters work, especially for noise reduction and such. It's even nicer if you can do a single opamp version. The math for it is a PITA, though an excellent numeric solution was published by Burr-Brown in their old, and out of print, Function Circuits book, albeit in Fortran. Here's my minimalist conversion that hopefully will be of use to somebody. It's the 4th item down.