The issue with quad video cards is the two slot space that the cards take up and when doing quad video cards it may be better to go with the 7990 card so you can get two cards on one two slot card. Then again I don't even know if they are making them. How about a pair of GTX 690's?
Anyway with four two slot cards tou need 8 slots to make it work or 7 slots and space between the bottom of the MB and the power supply so the bottom card fits. Then you need a motherboard with the right slot layout that will allow the four cards to be put in all together.
The case looks like it will work and the next question will be the MB and the slot arrangement , there's a good chance that the bottom card will cover the bottom row of connections and all of those connections will have to be made before the video card is put in.
Most mid-tower cases only have room for 7 PCI slots, While most full tower cases will support 8-10. I'd be looking at a full tower case for 4 way crossfiring of 7970's. The COUGAR Evolution Black at $80 is NewEgg's least expensive full tower (has 8 PCI slots), http://www.newegg.com/Product/Product.aspx?Item=N82E168...
the prices go up rapidly from there
Hope it helps
You could only if you water cooled them (which i'd advise doing for 4 way) depending on the connectors on the card. For instance you could put 4 of these in there http://www.newegg.com/Product/Product.aspx?Item=N82E168... but you'd then have the problem of radiator space. You would almost certainly have to go for an external arrangement.
$999 if you finish reading the review
Looks the same size as my 6950 DCIIH20's
definitely a full or supertower job if you go for quad cards,
You would need a decent sized rad to cope with the heat, which would be an external mount as well,
Are you sure you are up to it?
is your wallet?