Hi. You have acquired some good prep materials, but you certainly do not need all of them. Here is what I recommend:
With four months to prep, use the MGMAT guides
. Cut the Kaplan
book from your study plan as it is less in depth. Use the OG 12
to support your learning of the MGMAT strategies. You can sub in the Powerscore CR
bible for the MGMAT Critical Reasoning book if you desire. Don't use both of those books as the strategies will conflict.Kaplan 800
can be used later in your prep once you have mastered most of the strategies. Or never, as it is not great. Notice that I told you books not to use. More books do not always yield more effective prep.
What is your starting score? Its impossible to tell you whether 700+ is reasonable in 4 months without knowing where you are beginning.
Finally, I strongly recommend you pick up my guide to GMAT self-study: GMAT Clarity (amazon link)
. It will ensure that you prep intelligently and maximize your score in the least amount of time possible. It was designed for dedicated self-studiers such as yourself.