...
I don't know it was a while ago.
Only you will know. My advice is to preview CD 4 sometime in the next few weeks and ask yourself, am I ready to move on? I would advise doing it anyway, because CD 4 is a good CD for growth.
I can't tell you how much improvement you will make, since I am not there with you or anything like that. If you work hard and do it everyday, there will be improvement.
Jolly Jake