I've worked on the Thermaltake Commander MS-II chassis with a Thermlatkae Water 3.0 120mm AIO watercoolign unit which is very similar to the H80 in a lot of ways. I had a hard time getting the cooler to mount+fit inside the chassis at the rear exhaust mounting location in the chassis and I had a harder time trying to get the side panel to close. I had to literally lie the case on it's side and then with my arms sprawled across the panel and edges had to nudge the panel on to the chassis's guides.
What's worse is that the top fan mounting locations are centered to the chassis which can and will interfere with the motherboard's heatsink's.
On another note, what is your full system's specs? Going for a watercooler isn't always the best...