the 3550p is the best bet for you. as your using a 3 party gpu for gaming. the 179.00 price tag is the best bet for you.
here windows 8 for the same money. http://www.tigerdirect.com/applications/searchtools/ite...
it going to be faster then 7 on most of the newer mb and ssd.
also look into tossing in an evo 212 cpu cooler..it keep your cpu cooler then the stock intel one.
Don't worry about overclocking if don't know how, read up do it next time, if it want to. Just a way to get a little extra performance out of your computer, but takes a bit a knowledge not to F it up and be safe.