49c idle or load? If load, you have nothing to worry about.
If that's your idle temp, it's pretty hot. The first thing you should do is worry about cooling your case. If you've got an intake and exhaust fan, try clearing cables out of the way that can impact your airflow. Do a google search for case cooling and you'll get some good ideas.
Instead of modding a 120mm fan onto your stock heatsink you should look into an aftermarket heatsink. At the top of this forum list there's a great thread with reviews. Check out the XP-90, it's one of the best all-around heatsinks for price and weight.
Welcome to AT!
-z