Or if it's a prebuilt? Get the CoolerMaster, Hyper TX 3 .
Then no motherbord removal are required. Ok. it does'nt have the 120 mm fan of the 212 model ( only a 92 mm ) and cools a bit less well than it's big brother. But the TX 3 is still way better cooling and noise vise than any stock cooler. This cooler fits any normal sized, mid tower case.
Reduceing the cable clutter inside the case , and making sure that as few cables as possible are out of the way from the intake to the exhaust fans, air flow path can also make a huge difference. And of coarce cleaning out the dust now and then. Especially when it comes to the cpu cooler, motherboard heatsinks and RAM. And also the video card + the fan case grills and the fans.