Guys, have a quick search on the Giel PC3200 ram reviews - you will see that these come with heatspreaders. Upon further investigation by the reviewers, they removed the heatspreaders to find out that the chips on the pcb where ddr266 rated. Yet, the Giel sticker on the heatspreaders said pc3200. So it is believable that heatspreaders can assist in running faster clocks more stably, I have samsung pc3200 with the thermaltake heatspreaders on them and can hit ddr420 fine - although the pc is not too stable due to southbridge chipset voltage problems (asus a7n8x rev1.04)
But you will find that apart from looking nice, they can offer some assistance - run ddr266 with heatspreaders and run them at ddr333... should work fine without additional voltage.
Cheer,
Vape.