After some research I've decided to start out with the 3Pi kit, and try to measure and adjust the crossover to the smaller box/baffle size. Or maybe just add some simple digital corrections with the Minidsp shd streamer/dsp/dac.
I think I will go for the B&C tweeter. Not sure yet which woofer. The B&C woofer seems maybe to do better in a smaller box (+ higher sensitvity?). Any opinions on which is the better choice?