I have xperience with both the FK-320 and the SX830, so I will try to shed some light on the topic.
The FK-320 is very sturdy and well-built, and the airflow is remarkable. The 92mm fan at the back with the shroud should blow air INTO the case, so as to provide the CPU with a fresh supply of cold air. If you have an Alpha heatsink, or any other where it sucks air off the heatsink, you will need to switch the fan around, which greatly comprimises the cooling abilities,m and you will be better off with an Antec case. Otherwise, the case is very well insulated, looks nice (I think), and is overall just a great quality case. However, the left side panel is a PITA to attach and remove. I mean, you really gotta give it a lot of muscle to move it. It is my only complaint with the case, but its annoying for one who messes around with the innards of his computer so much.
The Antec SX830 i also very well built, uses drive rails, has 3 spots for intake 80mm fans in the front, and 2 80mm exhaust ports in the back. Excellent airflow. It, like the FK-320, uses removeable drive cages, but I like FK's method better; is much easier. The SX830 utilizes a wonderul "door" swing/hinge method to open the case, which is simply beautiful. It is so easy to remove the side panel. Its like a dream. I really really like that feature. The case sides feel a bit flimsier than the FK's to me, although this may be unfounded. Both are very sturdy and heavy. You cant go wrong with either.