I would recommend like others to get 50 or so dives behind you. This gives you some time to think about the ow and aow course and become profecient in the skills. More than that it provides many opportunities to talk to other divers and solidify what you learned in ow and aow along with listening in on discussions about deco and notrox and partial pressures in ways you could not while in ow and aow class. By this point you should be well on your way to good buoyancy and posess a greater confidence in your abilities. This is when you can jump into nitrox and get the max benifit from the course. Prior campfire talk will allow you to learn intelligently about the world of other than air diving. Once you have that done and after another 20-30 dives experiencing various problems or witnessing other divers having problems you are ready for courses like stress & rescue. One can always read about panic ect. but when you actually experience it your self, you are forced to ask why it happened and how you could have prevented it. After all one of the best ways to prevent an OOA situation is to make sure you have air at your mouthpiece at the start. Not being sarcastic its real world. If you know how it hapened to you then you know what to look for with your buddy better and hopefully your buddy for you. Rescue comes in to play when all else has failed, for the most part. No course can effectivly teach you how to do pre-emptive strikes on at depth failures. Not till you see your share of dropped weight pockets, dangling tanks, abrasions, jelly fish stings, over and underweight situations ect can you appreciate the value of stress and rescue class. Go out and experience diving for some time so you can bring those experiences with you to follow on training.
Regards
