For a good 4-axis unipolar board kit, I can recommend the Xylotex board (I got mine running last night for the first time). The HobbyCNC board is also available and very similar to the Xylotex board.
For your motors: As far as I know, your motors should be able to be used as unipolar or bipolar motors - 6/8 wire motors are quite versatile. I think (someone else, please verify this) you basically connect the centre taps from each coil together and then use the 'outer' wires from the coils. This effectively gives you a 4 wire motor.
Good luck with your router - CNC is LOTS of fun!!!