I agree, you will know when it is the right time. Whether now or later you won`t be replacing Quincey, he will always be in your heart as the unique boy he was, rather you will have another pup with his own personality and his own corner of your heart. I know that is how its been for me.
Just thinking back I think I tried all three ways, not getting another dog, getting one almost straight away and waiting a little while. We had our GSD Duke and our mix dog Blue when our Dobie Prince had to be put to sleep, while not yet a year old, and we got another Dobie, our Max, about a month later. When Blue was put to sleep we didn`t get another dog. Nor when Duke died. We then became and stayed a one dog family.
I was living a whole new different life by the time I lost my beloved Max, I was a widow, out at work, my son grown with a wife and one year old daughter, a whole family of his own. It was so hard for me then, coming home to an empty house, no Max to greet me. After after a few weeks or so I couldn`t stand the emptiness any longer, I got a 6 month old female GSD, Penny. She became very precious to me and helped me to live without Max. When I lost her I wasn`t at all sure about getting another dog at all, just the thought of going through that pain yet again at some point in the future. But life without a dog was just too empty for me so after a couple of months I got my Bob.

Sobbing, when does that stop? Give it time, it will. But you will always cry for your Quincey, not all the time, but every now and again something will remind you of him and you will shed a tear. But there wil be smiles there too, when you remember some of his ways and antics. He will always live in your heart.

My thoughts are with you and your wife, and for Callihan too. Hold on to each other.
Love and hugs, lots of them.