I recently built a bookshelf 3-way with purpose-made passive crossovers using the following found at Parts-Express. I can give you the crossover schematic if you're interested. I'm really astonished at how good they sound for the money I spent building them:

Dayton Audio ND25FA-4 1" Soft Dome Neodymium Tweeter ($15)
Dayton Audio RS52AN-8 2" Dome Midrange ($41)
Dayton Audio DCS165-4 6-1/2" Classic Subwoofer 4 Ohm ($43)

Crossover frequencies I used are: 500hz and 3.0khz

Good luck with your project!