For blender use a gaming card instead of a workstation.
It can be upgraded but the processor and memory should be good for quite a while, by the time you need to upgrade the processor newer stuff will be out and would make more since to start over. You can always add another set of memory in the future if you need to.
I upped the power supply to handle a higher end video card in the future, but the GTX 960 4GB version will be a good start.
Goes a bit over budget but you should like the performance.
EDITED build the price on that motherboard went up 50 bucks.
http://pcpartpicker.com/p/pQKzrH
Join their forums and post the build their and get some feedback from the people that use it, they can also help you with problems! http://blenderartists.org/forum/