I highly recommend buying Wayne's prebuilt crossovers. They are well built with high quality components. Also, the markup Wayne puts on them is very little in my opinion. He could be selling them for double, but keeps them at an extremely low price. You also don't have to worry about messing anything up in regards to component selection and wiring. It is also a small way of giving back to Wayne for such an awesome free design.
Now if we could get a surround speaker with compression drivers, I'd be all over that to complement my 4Pi's =)