You can only buy Scratch Cine as a turn-key solution integrated with a highly tuned, specially optimized workstation.
Aside from the whole Windows-vs-OSX silliness, there is no MAC Pro, HP or Dell on the planet capable of the performance required to reliably decode and output .r3d at HD or 2K. The reason is simple. All those systems are too slow.
Also, obviously there is no solution for HDSDI output via NVIDIA Quadro on the MAC right now anyway.
It's great that Scratch runs in Bootcamp, but frankly, without full hardware support. it's a mostly just an academic endeavor. You won't be able to do much beyond simply conforming your r3d stuff. And there are other tools for that which might be more cost-effective on a MAC.