IMC - Do this as soon as - this is a potential life saver, and is can be used at any stage.
Tailwheel - don't bother with unless you intented to fly tailwheel soon afterwards. Decide now whether tailwheel flying is going to be a feature of your professional career, and if not, steer clear of taildraggers altogether.
Aeros - Do this after the IMC. The unusual attitudes practise and aircraft handling will set you up for life. Don't worry about picking up bad habits. If you survive solo aeros, it can safely be said you have not picked up any bad habits.
Complex - Do this as close to the CPL as you can.