I for one went and added the progressive Heavy Duty rear shocks and replaced the front fork springs with the progressive springs.
I will agree with everyone that the stock rear shocks will work OK for you as long as you up the preload, but by adding Heavy Duty shocks you will notice a handleing and ride improvement.
Regardless of your weight, but especially because of it I cannot recommend replacing the front fork springs with the progressives enough. Normal sized people (unlike you and me ) rave on the handling improvement, and for us bigger fella's, it is just amazing. No more nose diving going into tight turns, and under heavy breaking there is significantly less nose diving. All around, for the money it is the most handling improvement you can do. New Progressive front fork springs only run around $70. While your replacing the springs go ahead and replace the fork oil too