2x12 is what I would suggest. I have one for both bedroom practice and gigging and it works well. Mines flex back, so I use the closed back for at home which sounds a bit better (better for recording as well), and open back for gigs/band practice as it tends to allow me to hear myself better and fills the room better - its not as directional..
I would like a 4x12 just because they look cooler, and probably have "bigger" bass, but they're too much hassle to move around and not really necessary unless you're playing metal imho.