Sorry Lance! That post was mine - I withdrew it when I realized I hadn't gotten my hands on that particular board....
My experience with SM is pretty variable -we continue to use them in situations where we need more than 2 physical CPU's.
My issues:
1) Spotty BIOS updates
2) Lack of any case / firmware management, basically your fans are either full on or not. Intel Server and Workstation class boards
offer excellent firmware options, including case Fan throttling, in fact the excellent Chenbro case you describe is a supported enclosure (note that the current Xeons do not offer closed loop operation, where Fan speed is control by on-die temp - the Core I-7 does - look to the next gen "Haswell" Xeon CPU's for this...).
3) Going with a 2 or 3U rack chassis is going to result in a very noisy machine. We have a pair of SM Quad CPU machines as Database servers in a regional health clinic's datacenter - hearing protection required.......
Obviously a personal choice, my workstation *must* be as quiet as possible, my customers strongly agree......
Finally, Premiere & PS CS6 currently only take advantage of a single GPU - multiple or dual GPU cards, at this point are pointless.....