Did you thought to rent servers on demand? Preparing an systems image and run it there? Charged by time spent and after finishing you can freeze the system.

It's not so cheap, but very flexible and I think when your doing such high-resolution render then it's for business.

There's only one issue, you could violate license agreement with outsourcing an image containing Windows + Poser + Firefly. 

Did you use Firefly or other renderer?