It all depends on what you want to do with it... I assume you are not watercooling? .. if so you may want to look into a larger case.. and maybe one that is already made for a watercooling system. ATX I assume... though they are very common.. there are alot of things that make a case...you can tell alot about the user by his computer case, lol
The Antec 900, though it is a tad on the small side, is an excellent case. I would get one but a lil too small for my setup. - I may even buy one as a project mod pc this summer.
Personally.. I would recommend the CoolerMaster Stacker 830 or the 832... the 832 has a built in watercooling feature I believe...
I think that the CoolerMaster Stacker cases have a little bit for everyone.. they have alot of growing room and have great air circulation. They make SLI a dream with room to spare...and they have a TON of features like tool-less installation and a removable motherboard tray...
I am buying the Stacker 832 for my new rig I am building "Project-X"
Here are links to pretty cool slightly modded stacker cases that may appeal to you:
My PC Rig: wreck's Red Stacker Computer
VirtualRain: Water Cooling a CoolerMaster Stacker 830
^ I love the black paint job.. I am going to paint mine black.
Custom Built Cooler Master Stacker 830/832 Side Window
Other than that I recommend Armor and lian li cases..