Max joined us in August of 2013 when he was 12 weeks old. At first Toni took him to work with her everyday. Her boss was OK with this but it turned out the landlord of the business complex she is in wasn't. We did not want to leave him home alone for fear of anxiety setting in so we were able to get his sister Sasha (from the next litter) in April of 2014. Best move we could have made. They are inseparable. Play together, sleep together. etc, etc.
I don't have any experience in uniting 2 older dogs but I do know that Max "adopted" Sasha 5 minutes after she came home. Taking in a dog who may not have had the pampered life that we lavish on our furbabies would be a fairy tale ending for that dog, but there is no "wrong" choice here. Whether it be a new pup or a slightly older one, it sounds like Crystal is going to have another "best friend". Good luck !