Thanks man, this was a first time build for me, needless to say I am feeling sorta proud of myself at the moment for just going for it in spite of knowing very little about it. Never again will I pay some schmuck to build a sloppy system for me (looooong story there....)
No overclock yet, I built it for overclocking but that's all new to me at this point. Hell, before last Sunday i was still reading up on how to apply artic silver and trying to figure out what a heat spreader was! I need to find some guides and bone up before I dive into that ocean...
Anyhow, I've been wondering about that heatsink myself, it's strange because it was not there in the early pics of this board, nor is it seen in pics of the reference board, and stranger still, it is not present in ANY of the pics of the board seen in my manual. Seems that it was a very last minute addition. All I can tell you is that on the board it is labeled "heatsink 2", not much to go on there.
The chipset waterblock is a Koolance GPU-180-L06, and it was no problem at all to install, though if I had it to do over again I would have probably used the GPU-180-H06. The block i used seems that it will block the second card slot though, not 100% sure because I had quite a bit of leeway to rotate it (maybe 30 degrees each way) before I tightened it down. If it does work with a second card though it is gonna be tight. Can't say for sure. I would recommend using the Koolance CHC-AO5 to anyone using SLI just to be safe because it is very low profile but that block is only rated for 30 watts compared to 180 watts for the ones I mentioned above. There are certainly other/better options out there for watercooling that chip besides Koolance blocks, I'm just not aware of them.