With that system then you will need a monolithic case, when you say 9k is that $,£ or Euros ?
Do you really need 4 x 7970 GPUs? What resolutions will you be running?
The only case i can think of for your needs, and yes you will definately need to watercool all those GPUs to keep them in check, is this case..
Silverstone Temjin TJ11B-W Full Tower Extended E-ATX Aluminum, Black with Side Window w/o PSUhttp://www.scan.co.uk/products/silverstone-tj11b-w-full-tower-extended-e-atx-aluminum-black-with-side-window-w-o-psu