I used the WUP option when I bought Mercury V8. Got Mercury V9 for free. WUP is where it's (if you have it at the right time).
On my machine, 64bit is installed here:
C:\Program Files (x86)\Waves\WavesV9\Waveshells\WaveShell-VST 9.0_x64.dll
Don't be fooled by the fact that it's in the "Program Files (x86)" directory. Waves is weird that way.
Now, what I did (which is non-standard) is I created a "Waves" directory in my vstplugins folder and copied the .dll there. That's where I point SONAR 64bit to. I just have to remember to recopy the .dll on a Mercury update as that .dll knows what plugs I use.
Of course you could just point SONAR 64 to the "install" directory (i.e. my example was my install directory).