To my experience, Samsung RDRAM is a pretty good for overclocking indeed. As Dee-ehn already said my PC1066 is overclocked to 1200+. To be exactly, I raised the FSB to 156Mhz (normal 133). Quadpumped, this is as much as 624Mhz FSB (<->533). Dual channel RDRAM -> 2 x 624Mhz = ~PC1250 RDRAM.
This overclocking is done on a Gigabyte 8IHXP (rev2.1) and you have the same board (be it on ~400FSB though, because of the PC800 RDRAM). I doubt you can "fool" the mobo and your memory by selecting PC1066 and a 533FSB, although you never know unless you try
Anyhow, you can always try to raise the FSB in small steps (don't forget to enable "over RIMM voltage" and your CPU will probably need some more Vcore too. (watch your CPU temp!!)
The modules have default aluminum heatsinks and they are sufficient for cooling in my case (standard air cooling).
On my other mobo (ASUS P4T-533c), the RDRAM runs at default speed (PC1066). Not because of the memory, but because of the CPU. It's a boxed 400FSB P4 2Ghz, but I "fooled" the mobo by selecting the 533FSB nevertheless. Now the CPU runs rock solid at 2,7Ghz on a 533FSB. I don't even have to raise the Vcore.
I can't get the FSB further than the 133 -> 533 FSB though, so that's why the memory runs at standard speed.