Building your own PC probably starts with selecting the type of case you'd like. PC cases come in all shapes and sizes with different configurations and airflow. Here's are some great picks to get your gaming PC underway.
With six front panel drive bays (four 5.25 inch, two 3.5 inch) and 7 expansion slot the NZXT is made to grow. The case is also lined with sound dampening foam that reduces CPU and case fan noise. Along with this are five internal hard drive bays 3 PCI-e SLI slots and two 120MM case fans that help maximize airflow. Finally, there are two side/front panel USB ports, one Firewire(IEEE 1394) and a headphone/microphone input jacks.
The Cooler Master COSMOS 1000 is an elegant case with a slick design and tons of room for all the PC gadgets you could want. It includes 5 front panel drive bays, 6 internal 3.5 inch bays, three 120MM case fans(front, back and top) as well as a top mounted media reader bay with 4 USB ports, 1 Firewire port(IEEE 1394), eSata and Audio jacks.