Hmm, nice build indeed.
The Obsidian 800D looks roomy and suitable for this kind of thing. However, a double fan rad is used here, not a triple one. And I doubt that there will be space enough to place it on the bottom.
If you look closely on those two pics, however, It looks like 3 120mm fans are meant to be placed at the top, which gives me the idea that a triple rad, like the PA 120.3 that i am currently in the posession of, could be fitted in that area instead.
What I am unsure of, would be if the large rad will obstruct the placement of the motherboard as well as other components in the case...