I have the same Vapor-X Tri-X Sapphire GPU as you, except the 290X version, so I can appreciate how large a card this is.
I went for an AIO cooler for this very reason.
You may also want to consider a Nepton 280L.
Similar to the H100i and X61, but for pure cooling capability the 280L is at or near the top of the list.
Please note that the LED on the 280L water block is white only and can't be changed like on the H100i and X61.
The H100i and NZXT will be quieter under load, but if you want overclocking headroom you might consider the Nepton.
Here are a couple of reviews of the 280L: -->
http://www.maximumpc.com/cooler_master_nepton_280l_reviewhttp://www.tweaktown.com/reviews/5911/cooler-master-nepton-280l-aio-liquid-cpu-cooler-review/index.h...Considering the H100i and X61, the X61 shows slightly better cooling on many reviews and has a 6yr warranty vs. a 5yr on the Corsair.
Just a thought.
MOTHERBOARD: ASUS Rampage V Extreme
CPU: Intel Core-i7 5960X
CPU COOLER: Coolermaster Nepton 280XL
RAM: Corsair Dominator Platinum DDR4-2666 C15 32GB
GPU: Sapphire Radeon R9 290X 4GB Vapor-X Tri-X OC
SSD: Samsung 850 Pro 1TB x 2
HDD: Western Digitial Caviar Black 3TB x 2
PSU: Corsair AX1500i CASE: Corsair Obsidian 900D