I'm using a pair of Xigmatek SD-1283 Dark Knight II heatsinks with my E5-2620's, and it meant a clearance had to be within 159mm. That was a very tough call to make, but worked well for my build, however to put it lightly, it's very cramped.
The NZXT Source 210 Elite that I'm using is 194mm wide, but has a significant portion behind the motherboard for hiding cables. The heatsinks just barely miss the side panel when closed.
That's an example of the clearance as best I could get it when I did the build. For the record, when I put the side panel on for the first time, it did rub some nickel plating off a single heatpipe on one of the Dark Knights, but since then, there has been no contact at all.
I would suggest picking your heatsinks first, and then finding a case that is at the absolute minimum 25mm more than the height of the cooler. This will ensure you have adequate room. It was hard enough for me to find heatsinks that fit properly so closely together with the sockets, much less fit in the case I picked.
It looks like wharrad has an extremely tight situation, just like in my case (literally).
|Dual Intel Xeon E5-2670v2--Xigmatek SD1283 DK-II|Asus Z9PA-D8--HR-05 IFX|128gb DDR3-1600 ECC RDIMM|240gb SSD, 640gb, 1TB, 2TB HDDs|nVidia GTX660ti 2GB|Antec HCG-750|NZXT Source 210 Elite|M-Audio ProFire 2626|Art TubeOpto8 with Smooth Plate Tube Swap|Avid Artist Mix x2|
A 9500GT with 1GB of RAM is the most pointless thing since NASCAR.