The link above is to a website for PC builds. You can build a fairly good and able machine for $600 if you really spread your money effectively. I'd suggest finding the general look of the case you want and narrowing your search from there. If you don't care about looks, go cheap on the case or buy an older model of the case you want.
Actually I'd wait until the min and recomended system specs are anounced. For several reasons: First off all you'll want to make sure the PC isn't just sufficient to run the game but anywhere between min an recommended specs to make sure you don't run into performance issues. Secondly I guess with not even in CB we are still at leat 6 months away from release and it won't be befor then that the specs are anounced. By that time you will get a much better machine for your 1000$ than you would get right now.
Rule of thumb when buying a new PC: Wait as long as possible to be happy as long as possible afterwards. Meaning You only want a new rig when new PC exclusive games start to not run smooth anymore. And then you wait until the next big title you absolutely must play is actually available.
In my language i have forums where you can just post topic with amount of money you want to spend and then they build your computer nicely. Try to find PC forums or something.
The specs aren't known yet, and with PC's it is always better to wait because new tech comes out making older tech cheaper, so the longer you wait the less you probably have to pay. Unless you see a bargain of course.