I don't know if you can buy just the case, but I prefer Alienware cases they are huge and you can get you hands in without ANY problems, can hold 4 optical drive with ease. And lots of locations for fans.
I also prefer Dell's XPS cases, a bit smaller but very well organized as far as route of cables, and with their instructions at their website very easy to add optical drives and hard drives. Two optical drives and two hard drives with ease.
My barebone new computer is coming next week and I will add the goodies.
XPS 8300
WINDOWS 7 HOME PREMIUM 64 BIT
INTEL CORE I7 2600 PROCESSOR 3.4GHZ
16GB DUAL CHANNEL DDR3
1TB 7200RPM SATA HARD DRIVE
AMD RADEON HD 6450 1GB DDR3 VIDEO CARD HDMI