I forget if the P5 uses the same rear subframe as the sedan, but if so you can buy the mazda kit for $360. comes with everything. bars, bushings, rear bushing brackets, rear endlinks and i believe front endlinks. MSP rear subframe, nuts, bolts, and an exhaust donut and gasket as well as instructions. Or if you get the AXR clunk fix brackets you won't even need the mazdaspeed rear subframe since the stock bushing mounts are not used.
If you are using the stock struts you will need the MP3/MSP or aftermarket struts because they have reinforced endlink mounts.
I bought the kit and axr brackets, i threw on the MSP rear subframe anyway tho.