Meguiar's Gold Class car wash is really good stuff. I've always been impressed with it.
There really isn't much benifet in putting AIO in your wash solution. Its not going to dilute and seperate like a soap is going to. It will also strip waxes off your car if you use it that way too. I would just stick to regular car wash if I were you. Its easier to come by, and like you said, less expensive to use.