Is there any particular reason why it needs to be an 1155-based board? The 1366 & 1156 boards are also viable alternatives. For a high-end workstation, I think the 1366 + X58 chipset is the best alternative.
Yeah, I agree that the 1366 is the best alternative. However, that will nearly double my budget for a processor. I was under the impression that the Xeon E3-1290 was socket 1155. I may even have to go with a Xeon E3-1280.
About the Motherboard well get the ASUS P8P67 PRO or the ASUS P8Z68-V PRO, these are the best right now for your budget. about the CAD well you need a QUADRO FX or a FIRE GL GPU's, in your case to make sure you will get the results your looking for.