Benchmark: Noise
The Carbide 400R is clearly capable of cooling high-end hardware, but Corsair's gung-ho approach to serious airflow does come at the expense of noise.
With the two pre-installed fans running on a silent profile the 400R is audible, but turn the speeds up and it becomes clearly loud. Having fan mounts on almost every side can be useful, but on the 300R the number of empty vents allows noise to leak out with ease.