For the price you will pay for a craptastic version of Vista to upgrade from....you are better off "from an IT perspective at least" the just go with a fresh new install of Win 7
Trust me, I'm A+ and Network+ certified....upgrading windows is trash and if you plan on building a new rig, just find a buddy who is enrolled in college and see if you can have him buy you a student version for cheap. If not.....a new version of Win 7 is pretty cheap now anywho.
PS. Make sure its 64 bit ...which I'm pretty sure all current versions of Win 7 are.