OCC has published a new review on the NZXT Guardian 921

The three fans equipping it perform well. They could have been spinning a bit faster, but noise would have increased. They are incredibly quiet at their speed, and they still beat a faster fan setup like in the Thermaltake Xaser VI VH9000BWS. But there is also a small problem having a third fan on the side. This one leaves little room for larger heatsinks such as my Xigmatek HDT-S1283 CPU cooler. I have to force a bit to get the panel closed, therefore pushing on the motherboard. However, if you plan on watercooling, you won't have any problems. The Guardian 921 even allows you to pass tubing to an external radiator by two holes at the back, especially made for that purpose. Moreover, a great feature which adds to both watercooling and air cooling setups, is the temperature reader with three probes. You can stay aware of any temperatures, simply by looking at the LCD in front of the case.

NZXT Guardian 921 Review