I am in same situation and what have decided to do is get a buggy board for back of stroller (got cheap on eBay) and wait and see when I get tired of carrying number 2 what stage DD is at. At the moment she likes to walk everywhere but that may change, she will still sleep in stroller, but I figure I can swap them round and carrying number 2 if she wants to sleep or if she is walking or riding on buggy board he can go in it. We also have a second stroller got given for free so if was out with DH all day for example could both push one if necessary. We have small car and use trams alot so figure double would be awkward so trying to get away without. Mind you I tend to leave all my purchasing to last possible minute as I find predicting exactly what bubs will need in future difficult and hate the thought of getting something not quite suitable.