Contrary to what Corsair states, the maximum GPU length for this case is a little bit longer than 290mm. The Matrix 980 is 297mm and fits like a glove. There are reports of people fitting cards up to 305mm in the case as well (Sapphire TRI-X OC). There is approximately 0.5mm to 1mm of clearance from the top of the GPU shroud to the inside of the top of the case. Just enough to get it on and not touch.
Short PSU cables were a huge help for cable management. Running the CPU power and front audio header under the motherboard were absolutely necessary.