CPUs nowadays can go much higher than 70°C, but I'd definitely try to keep them around that mark for the sake of not turning your room into an oven.
Thanks for the nice comments and sorry for the late reply. I agree with you and I should have actually covered that to some detail in the article. A workstation board should suffice no problem. The RAM issue is a good one too... I am unsure why Intel limited the maximum to 8GB on this board when 128GB is the maximum for the same 5400 workstation chipset.
It definitely all comes down to what you need the machine for, and in your case, what you laid out seems to make perfect sense.
If you have absolutely no use for a graphics card, then getting the cheapest one possible is fine. I'd just recommend getting one that's at least PCI-Express and around the $40 range... so if you choose to move up to Vista later, you can use the basic features while setting it up.
As for the calculations you are doing, the software doesn't support 64-bit?
As for workstation boards, I don't have any recommendations, but the fact of the matter is, any workstation board out there that's dual-socket LGA775 will be able to deliver what you need. You are not using the machine for enthusiast purposes, so any reasonable workstation board out there should be fine. Sadly, I really don't have a recommendation, as it's not an area I'm familiar with. Two brands worth checking out though are SuperMicro and Tyan.
Thanks for the compliments Daybringer! Xeon's are the server-equivalent to the desktop processors, so there are virtually no differences in terms of what will run and how well something will run. If you see a Xeon and desktop processor with the same frequency, cache size, FSB frequency and et cetera, you can be sure it's the identical chip... just with a different name.
An update on my system:
I think I am upgrading to two GTX 280's
If that still doesn't give me the performance I am looking for I might get a third. Intel supports tri-sli with their new bios update.
Ahh, it's nice to know that Thermalright sells a kit like that. You are really getting some great temps now... I wish my Skulltrail was so kind.
Edit: Hah, I found the link. http://forums.overclockers.com.au/showthread.php?t=714778 Check out THAT Skulltrail build... blocks and all.
The memory is another thing that is beginning to bother me quite a bit. Not the speed, but the fact that the modules themselves heat up so much. During normal use, the center chip on the FB-DIMMs hit around 70C (I tested this with a reliable temperature diode)... which is clearly asinine. It might run stable, but it sure does a great job of adding heat to an already hot machine.