Ditto hearts... I think you should foster the dog you'd like to adopt for a few days to a week to see if their "personalities" match. Expose him or her to as many common household scenarios as you can, and bring him or her around some kids. The
best combination of dogs you can get is two that are calm, easygoing. Helps if they're both submissive (to you, of course). It's hard to tell until they get used to your home; and I'm sure you know that with rescue dogs, behavioral problems are
common.
Years ago I had two, and they just didn't mix well. One was very calm but tended to dominate; and the other was submissive, but very high anxiety. They would get into squabbles a lot. We ended up finding a better home for the high anxiety dog,
where he would have a job to do on a farm. The other one did much better on his own.
Best of luck - I would love to have two again, and probably will when we get a larger place. :)