Rewire not available in Sonar 8.5 and Reason 5 with Windows 7 64 bit

Are you using SONAR in 32 bit? You can install both versions without issues on the same machine, but I suspect you may be trying to use the 64 bit SONAR with 32 bit Reason. I do not own Reason, so just speculating here... Not sure if this is an issue.

I loaded SONAR 7 when I got my first Win7 64 machine and quickly shifted to the X-series.

I can confirm both answers. Either you need to use 32-bit versions of SONAR and Reason, or 64-bit versions (in which you'll need to the 64-bit ReWire dll).
 
Reason still makes a great instrument rack for SONAR 

I would definitely recommend using the Mackie 64-bit drivers over ASIO4ALL. 
 
Another option is to take advantage of the current upgrade price to X3, and get Reason Essentials. Then if you want the other Reason instruments and such, upgrade to a full version of Reason in the future.
 
The 8.5 vs. X-series issue has been debated here quite a bit. I think it's fair to say the consensus is that there's a significant learning curve when making the transition. Some people are happy with 8.5, so feel there's no need to change. Some people like particular aspects of 8.5 which are not in X3 and therefore are sticking with 8.5. Those are both valid, "if it ain't broke..." attitudes IMHO. However, I do think the majority of people who've made the switch and become comfortable with X3 would not want to go back to 8.5. There are several standout features in X3 like the comping, ARA/Melodyne integration, ProChannel, VST3 support, better plug-ins, screensets, superior workflow, etc. that are extremely compelling.
 
It's good you're checking out the trial X3 version, as that will allow you a more informed opinion. But do keep in mind it will likely take the full 30 days to get a handle on the program.