It's a Silverstone GD07B, a flat HTPC case which presenting some problems due to low height. I'm probably working with roughly 5.5" of clearance (don't have a tape at the moment).
So far, I'm wondering if my best bet might be the Scythe Rasetsu (http://www.scythe-usa.com/product/cpu/113/scrt1000_detail.html)