The exact chip I plan on getting is the AMD Phenom II X3 720 2.8GHz Socket AM3.
What is a good aftermarket fan and heatsink combination to go with this. I can't find any that say they are for the AM3 socket, only the AM2. Will the AM2 work? (I've never observed either). Any opinions on what to get would be appreciated.
Your best bet is to visit the manufacture sites, Scythe, Zalman etc. and check there. I believe that if the cooler works with AM2 then you should be good for AM3. The only difference is the number of pins.