M.Y.
I had the single valco for my first child and had bought it thinking I would later use the toddler seat when I have a second but decided against it. I had heard from others who had it that the stroller tips over rather easily with the older child in the toddler seat. I bought the valco double and love it. My only complaint is that it is a little wide but they all are (side-by-side doubles). The MOUNTAIN BUGGY might also work for you...I really wanted to get this one but my oldest was too tall for it. Good luck!
PS: I feel like the P+T is not as good a quality stroller and I also didn't like how low the baby would be...