there are plenty of HS suggestions on the forum why don't you take some time and read through them?? better yet, visit google and search "heatsink reviews" will net you plenty of good results.
to answer your question, the stock heatsink will do its job, and thats about it, if you do not overclock, and is OK with the noise level, you shouldnt be too worried. however, replacing the stock sink with a better solution is always a good choice.