I've had two girls and I've had a girl and a boy, and I've had solo Basenjis. Two are definitely company for each other, and are a great idea if you have to leave them alone for any length of time, but it definitely changes your relationship. In my experience, the second one will generally be more attached to the other dog than to you, unless of course the original doesn't like the addition (happened to me when I added a boy. My girl hated him on sight, but did learn to tolerate, if not enjoy, him. She would never play with him, however). I find I do more training for fun and spend more quality time when it's one on one.