YES, adding an aftermarket cooler would be very beneficial. Idle temps are not really a concern, load temps are. You should see a substantial drop at load with something like the 212+ to warrant the $30 cost.
Coretemp or Realtemp for monitoring your temps will work.
COOLER MASTER Hyper N 520 vs COOLER MASTER Hyper 212 Plus which is better?
Which on will give me better load temps?