Except for Rebirth, Reason's dad, so to speak, I don't think there is anything. It would run nicely on your 6400, though, but all it gives you is two synths and some drum samplers. It's great, I made my first beats with it 10 years ago, but it's not really something you can make full productions with without some clever layering.
The fact of the matter is that up until five years ago and even more so when your computer was new, people were still using external synths almost exclusively. They had to, because the computers weren't powerful enough to run a number of synths and samplers and effects and mix it all in software in real time. Ten years ago harddisk recording without extra hardware was still a new feature in most professional music software, and my old 8600 struggled with more than eight tracks, as far as I can remember.