Here is an update. I dropped in the Black Knight, it fit well, but just barely. I was hoping for something that wasn't so massive, but it looks like your advice is good.
Here is a shot from a different angle:
And, while I had the motherboard out, I figured it would be a good idea to enhance the exhaust air flow. Especially with the big heatsink in there. So I removed the case material where the rear fan is and installed a grill. Not the best job, but it works. (Notice the lack of PS/2 ports for the motherboard and mouse)
And last but not least the test results. This is after processing video at 95 to 98 percent CPU capacity for about 20 minutes. Looks like about a 10 degree celsius improvement. A much more exceptable max temp.