Oh - this has can of worms written all over it!
The AC Freezer 7 Pro comes with a very thick lump of thermal paste applied to the base.
There are 2 schools of thought on this.
School 1 (my alma mater): The thick paste is designed to allow for any imperfections in the finish on the CPU heat spreader and cooler base. The thickness of the pad creates a filler with no air bubbles and gives the best possible contact between cooler and CPU.
School 2 (old school AMD): Anything more than the thinnest smear of arctic silver 5 is the work of the devil and the supplied thermal paste should be scraped off, then the CPU and cooler base should be lapped and a thin smear of AS5 applied to the heatsink.
In my opinion, the TIM supplied with the AC7 is excellent and you should fit it carefully the first time and it will work fine for you. You don't need to buy any extra AS5.