Okay, here's an answer by someone who isn't drunk (yet)
Arctic Silver 5 is just about the best thermal paste, BUT the difference in temp will be only a few degrees at maximum. Thermal pads are not very good, but since the whole business only makes a small difference at most you can use them too.
I recently brought back my temps from 73 Celsius (yes that's very hot) to 48 degrees, both under 100% load. The only thing I changed was
1) blowing out all the dust that had accumulated between the individual pins of my Alpha 8045 heatsink, this gave me about 20 degrees
2) lowering the voltage of my CPU until the level just before it began failing Prime95 (excellent utility to make sure your cpu is running errorfree). This gave me another 5-7 degrees, my Athlon 1700+ cpu is now running at 1.575 V instead of the standard 1.750 V.
I also used Arctic Silver III but that never made more than a few degrees difference. If your cpu gets hotter and hotter after a few years use, make sure it isn't dust clogging up your heatsink.
Okay, done talking, time to get loaded