The Reason Synths are actually pretty chill. I used to run Reason 4 on an old AMD 1.8ghz notebook with 512 ram and I never had an issue. These Reason 6 files are bigger but still not too taxing by any means. It's when you're loading tons of effects and the new Rack Extensions that you start running into trouble - at least that's where I am now.
I have a 2.5 ghz Intel Core 2 duo with 4gb ram. If your computer is faster than my MBP notebook, then you are totally fine for the time being. I have some pretty monster tracks right now and even after really cleaning up and streamlining my rack the best I can, I run into issues but can work around things for the time being.