Sorry this happened to you.

I think using a cable lock and a U-lock in tandem (pardon the pun) is a good idea. But I would recommend putting the U-lock through the rear wheel, frame, and the bike rack. Then use the cable to secure the front wheel to the frame ... and continue around the bike rack too if it's long enough. Even if you keep the next one on a balcony, I'd still look at keeping it locked up.