The Cross 28 will work as well. Basically, tubes have a lot of stretch so a tube rated to 25mm will work on a 28mm (that's what I was running on my commuter because I was too cheap to buy new tubes when I went to 28s on it). If you are near (or slightly above) the max size, the tube will stretch more and, therefore, be thinner. If you are near the minimum size, it won't stretch as much and will, therefore, be thicker. (Of course some tubes are made thicker than others so what you end up with will be a factor of the type of tube and its size.)
The two other factors in tubes are the valve type (presta or shrader) and stem length. If you have shrader (like on a car), they usually don't come in different lengths. If you have presta, there are a lot of different lengths depending on your rim (deep rims need longer valve stems).