Sometimes you don't want your system to sound like a clogged vacuum cleaner, and that's where a silent case can help. To be fair, all cases are silent until there are running components inside (it's been scientifically proven), but with enough insulation and some quiet fans a case can provide virtual silence with a system installed and running.
The Silencio cases from Cooler Master have been around for a while, and the current iteration comes in both mid and mini tower versions. The mid-tower Silencio 652S was just reviewed over at The Tech Report, and it looks like a solid option for a quiet case without being too expensive at around $119.
The features and price tag of this case compare favorably with Fractal Design's Define R5 enclosure – recently reviewed here at PC Perspective. The 652S boasts massive storage capacity for up to 9 hard drives or 10 SSDs, along with support for long GPUs and liquid cooling, making it a nice option for quiet cooling depending on performance.
Pretty clean looking build you have there, Cooler Master
The case looks good if you like a minimalist design, though the review did find the included fans to be a bit loud. Check out the full review over at The Tech Report for a detailed look at the Silencio 652S.