Not a big PC user but you may want to skip over Vista and go to Windows 7. I believe that you can get the beta for free and upgrade to the full version soon. Can't speak for its color management capabilities but as an OS, all fronts point to this being significantly better than Vista.
Also, I would think for $2K, you'd could get a fast machine and a monitor you can calibrate to get good color.
for your budget you can easily get a computer that meets your demands i would recommend a Dell, HP, Asus, Fujitsu Siemens or Mesh Vista had its issues but 99.9% of these issues have been ironed out with service packs and updates as needed so compatibility etc shouldn't be an issue all you need to worry about s dual monitor support and for this you will a computer that has a graphics card that supports this hope this helps
core i7 any motherboard will do it doesnt matter.... 6gb of 1333 ram(or 12 will be best) 2tb of hardrive space and a gtx 285 this will last you for a long time
If you are close to an Apple store, you have to take a look at the iMac. A great computer that will blow you away. I think you would be making an enormous error in staying with Windows. You can buy all the Adobe programs and Microsoft programs for the Mac and the documents that you already have will work just fine.