Definately look for reviews before buying your specific Brix model/CPU. Some are quiet, some aren't. Anandtech on the Brix Pro
The presence of the Core i7-4770R in such a small form factor / chassis left us worried initially. We were wondering whether the unit would be able to properly cool down a 65W TDP processor within those constraints. Due to the size of the system, the fan had to be pretty small and rotate at high speeds for effective cooling. With a maximum speed of 4090 rpm, the sound from the unit was similar to what one would expect in a mini-server room (matching the noise from the Netgear GSM 7352S that we have running in our NAS testbed). While running various benchmarks, the speed topped out around 3900 rpm.
The unit does seem to throttle under full load of both the CPU and GPU (an unrealistic workload, admittedly, but one which some of the other systems we have evaluated have passed with flying colours). Now, the results that we obtained for the four passes of our x264 benchmark run were pretty consistent. It might turn out that normal workloads don't trigger the throttling and it is something we hope to evaluate further down the road.Techspot on the IVB Brix Mini
The Gigabyte Brix consumes very little power as its mobile Core i5-3337U pulls just 12 watts at idle, almost 3.5x less than the Pentium G2020, and only 37 watts at full load, nearly 40% less than the G2020.
When left to idle, the Brix operated at just 39 degrees, which isn't bad given how thin its heatsink is and more importantly, how quiet the whole system is. However, its temperature quickly soared to 78 degrees when under load via Prime95.