When peering in through the top panel, the HAF Xb looks much like a mid tower sans drive cages. The two 120mm fans are positioned to blow air over the entirety of a standard ATX motherboard. One thing that would have been a cool inclusion could have been adhesive rubber feet or possibly feet built into the side panels that would allow the HAF Xb to stand on its side so you'd have a bit more flexibility in your system's orientation. The top panel, which has a large mesh vent, has mounting holes for a single 200 mm fan, which would ensure plenty of airflow while keeping noise at a minimum.
Removing the two additional side panels turns the HAF Xb into an open air test bench. The lower drive bay is also revealed. The metal chassis frame has an additional bracket to brace the built-in carry handles on the side panels to ensure they wont give way to the weight of your system. Removing the front panel reveals the two 120mm fans, which are mounted on the outside of the chassis so that a 120 or 240 mm radiator can be mounted on the inside of the case. The holes are already thoughtfully placed so you shouldn't have any trouble mounting a radiator. Depending upon the thickness of the radiator you choose, there should be enough room to squeeze in a second set of fans for a push-pull configuration. There is approximately 3.25 inches from the front of the chassis to the motherboard, so with thoughtful cable routing you've got about 3-inches of depth for a radiator and pulling fans.
The bottom chamber houses the drive bays and power supply. The X-dock bays have a PCB mounted at the back which powers both drives, which slot in cleanly from the front, and also has SATA connections for each to run to the motherboard. Behind the X-dock is the power supply mount with a raised platform and rubber standoffs to minimize vibration. The lower intake is also filtered, as previously mentioned, to keep dust intake at bay. This creates a good thermal isolation of the power supply from the rest of the case as it intakes cool air and exhausts the warm air directly out the back.
Tool-less drive bays allow SSDs to be quickly clicked into place in a convenient SSD drive bay. For traditional 3.5-inch mechanical hard drives or 5.25-inch optical drives, a tried-and-true design is used by Cooler Master to allow you to easily slide the drive into position and flip over a lever to lock them down. The tool-less feature is clearly labeled so it should be clear how to use it.