http://pcpartpicker.com/user/OceanMonkeys/saved/2UZl
You have a K series processor so I am assuming you are overclocking, if you are overclocking it might be good to invest in one otherwise just save you money.
Yes, it is always good to get an aftermarket cooler. A nice air one will be quieter and perform better. Doesn't have to be anything to crazy though. Especially it you aren't doing crazy overclocks.
If i were you i'd get a coler, the cooler i got with my phenom 2 x4 was driving me crazy because it was so loud. And you need a cooler if you're going to oc.
i would think an evo hyper 212 would be enough if you plan to OC. I oc-ed a phenom black 965 on one of those and i got 4ghz so you should easily hit 4.3 if not higher if your air flow is good. If you dont plan to OC then dont bother with that chip, get a locked one that has a considerably lower TDP with a slightly lower clock rate and run the stock cooler.
+1 on Hyper 212 EVO.
If for some reason it's five bucks too expensive, the Hyper 212 PLUS performs just about the same. It may perform 1-2c warmer, but the difference is minimal.