Actually to be honest, in terms of processor, the new intel core i7 processors are the best all rounders processors available out there . However the only Intel board that currently supports these new processors is the DX58SO. Other manufacturers also have this X58 chipset on there boards so if you want some other board that the DX58SO you may have to search from the manufacturers site.
One thing I can guarantee you is that the Core i7 processor is a very good processor series. Best one available is the Core i7-975 Extreme, but the i7-920 will also be fine for you I assume and it's not so expensive as the extreme ones.
If you get a Core i7 processor bundled with an X58 chipset motherboard and triple channel ddr3 memory, you can achieve a very good performance for the kind of work you will be doing.
I cannot comment third parties motherboard having the X58 chipset as I have not used any of them yet to experience it. But I know there are many other board with the X58 chipset which can in some way be better than the DX58SO.
Hope this will be helpful to you.
I agree with the suggestion by Unplugged_24. Now if you want more information, how the nehalem cpu works on the Smackover board. Feel free to check this. You will see that the CPU Core I7 is really amazing for Mathematics Calculation.
Do your research before buying anything. That's the best advice i can give you.
All the best,