Its a little early to be doing an exact spec build since black friday can offer some great deals if you have the money by then and who knows what info will be out in the next 2 months from camp nvidia.
But for your budget, you're really not limited to any of the good choices out there. The i7 860 is a good choice, but if you want future upgrades, the i7 920 might be a better option as there will be 6 and 8 core CPUs out within the next few years and prices should be attainable. If you want that kind of upgradeability, then get an X58 mobo and the i7 920. Should OC to near 4ghz.
Other than that, just look for a case you like the looks of that has the features you need.
Is nvidia vs ATI an issue for your work? You're not doing any heavy gaming, so don't really need to spend big bucks on the GPU. A single card solution should be fine so a 500w-650w PSU would be enough. If you want the option of multi GPUs, then a 750w+ would be better.
Do some homework and repost when you're ready to buy so specific parts can be recommended based on price.