I would re-test that using some real 3d game on high resolution.
These are "defaults", power set to minus 20, RPM set to maximum - rest is automatic.
Stress test settings:
MSI Kombustor - 1920x1080
Stress generation is Power Capped.
Ambient Temps: 21°C
IF temps on -20 settings even reach throttling temperatures in scenario above, the cooler would be inadequate. The goal should be to reach similar temperatures on Power +-0%.
This indicates that stock cooler is actually quite good, however it needs to be lapped and used with proper paste. This is fresh Arctic Silver 5, i applied it about an hour ago so it will need 2 more weeks to cure.