There are a zillion options for thermal transfer from the CPU to the heatsink. Stand-alone thermal pads are crap - they dont even dissapate the heat evenly and once you remove the heatsink the pad is destroyed.
Thermal grease (gel) is a great option but it can cure over time if there is any space betweeen the CPU and the heatsink. I am a fan of phase-change material. When the CPU heats it up it turns it to a gel and covers the entire cpu and bridges any air gaps you may have.
The only downside is once you remove the heatsink, it need to be reapplied.
