We finally decided on getting one of the "travel system" ordeals where the stroller and the car seat combine into one unit and so forth. It wound up being cheaper overall than getting a separate car seat and stroller and that was the deciding factor. It's a pretty fancy looking thing all put together if you ask me, but what do I know.
I think we are going to keep the stroller part upstairs so that Holly can use it for taking Jack on walks and stuff without having to heft it up the stairs to use it, and without having to take it out of the trunk of the car.