Antec 1200 is possible.
Zalman VF3000F on a GTX480 is a 3-slot setup. See pic 1.
Motherboard EVGA X58 E760 has good PCIe slot layout. See pic 2 for a simulation. Card 1 will be installed to topmost slot. Card 2 to be installed on the 3rd PCIe slot (ie slot '6' shown in the pic). This leaves one empty slot in between the 2 cards for ventilation.
The lower card will extend beyond the bottom edge of the motherboard. Usually this calls for an 8th PCI slot case opening for ventilation. However, as pic 1 shows, VF3000F on GTX480 does not need that slot opening for ventilation. So, this passes.
The final check is that there is ample space between the lower edge of the motherboard and the top of the PSU, allowing ample space for ventilation for the lower card. See blue arrow
in pic 3.
In short, Antec 1200 should work, but might not thermal optimally as there is a challenge ahead.
One end note:-
But I give a head start of a challenge coming ahead. As the VF3000F intakes cold air and exhausts hot air in its own way, you need to devise a cold air supply path as well as an exhaust hot air escape route for the 2 cards. As pic 4 shows, VF3000F dumps heat via its top (and bottom) side, as dictated by the orientation of its fin structure.
Edit 1: I would usually recommend a 'top-exhaust' approach to handle cards dumping heat inside a case. But as the VF3000F does not dump via its front (and rear) but on its side, this calls for a different approach. I would not go too far off topic here to discuss that approach here and now and would rather wait until later on another thread.Edited by windfire - 5/26/11 at 8:56pm