Comparing with dual stock xeons already running at 2.83GHz...
I am actually thinking about putting together a very similar system and my budget is indeed around $2500, so your article came perfectly just in time and right on target. The purpose of the machine in my case is image processing and computations, not gaming. Therefore in my case one 8800GT or even new 9600GT would be just good enough and no SLI is needed.
Because of that, when I looked that you had to upgrade several components to get overclockable SLI machine, in my case I could, for a very similar total amount, go with a simpler board (dual workstation - but not server - board from Tyan or Supermicro or non-overclockable Asus). The advantage of such dual workstation boards over Intel's skulltrail mobo is that you can actually put more memory as you have 8 slots instead of 4. I could also get lesser power supply and coolers since no overclocking is planned.
The saved money can then be invested back into upgrading to 2 x ES5430 (~$200 more per CPU) or even 2 x E5440 (~$400 more per CPU). As the E5430 runs at the stock speed of 2.66 and E5440 at 2.83, one can this way build a workstation that would have the same performance as your overclocked rig for about the same budget - but without trouble of overclocking...
Again, this could work for me as I am not a gamer - if one wants top gaming results as well, different story...
Big thanks for great work!