32-bit softsynths in Sonar 64

32bit softsynths work in SONAR x64 via BitBridge.
 
Even though Cakewalk Sound Center is a 32bit softsynth, it should be working in SONAR x64 via BitBridge. Sound Center works fine for me and I use SONAR x64. So maybe you can be clearer on what you mean when you say "...However, that one actually works, unlike Cakewalk Sound Center." I know you mean that Perfect Space works, but you seem to be saying Sound Center is not working for you.
 
What exactly are you experiencing? Can you add Cakewalk Sound Center to a project, but you can't load a sound (program) into it? Or if you try to add Cakewalk Sound Center to a project, it wont load, and you get some kind of error message? It's not clear what you mean when you say it's not working. If you would be clearer about what you mean, maybe we can find out what's wrong.
 
Cakewalk Sound Center should be working in SONAR x64 via BitBridge or via jBridge, if you bought jBridge and choose to load Sound Center using jBridge. You can try re-installing Cakewalk Sound Center, and do a re-scan of existing plug ins to see if you are able to use it, after that.
 
Are you referring to the Cakewalk Sound Center Yahmaha Conservatory Grand piano sound pack when you say "...I would like to buy the Yamaha grand while it's on sale..." If you are referring to a Cakewalk Sound Center Sound Pack, any of them should work with Cakewalk Sound Center in SONAR x64.
 
 
 
 

I expect if you double check the X1 Studio installation, it is actually 32bit. Cakewalk Sound Center DropZone, RXP, and rgc Audio Square1 are all 32bit synths with no 64bit versions. Not sure about Session Drummer 2 but I imagine there is a 64bit version of it in X1. This is one reason why I believe the X1 installation is actually 32bit. I am pretty sure the browser in X1 Studio uses the same code as X1 Producer and 32bit plug-ins should show 32bit at the end of the plug-in name, if running the 64bit version of X1. The fact the plug-ins lack a 32bit indication in X1 is another clue the X1 is 32bit. I believe the 32bit X1 installation is why the CSC is throwing the IDS_MULTISAMPLE NOT FOUND error. There is a problem with the registry entries for the CSC installation and the actual location of the the files. 
 
If this is the case, the easiest fix may be to uninstall X1 Studio and X3, then perform a clean re-install of X3 using the instructions http://www.cakewalk.com/Support/Knowledge-Base/2007013371/SONAR-X3-Clean-Install-Instructions Also clean up the X1 registry entries. Then run the X1 Studio installer using the advanced install option if you really want Session Drummer 2, although X3 bundles the successor Session Drummer 3. Once everything is reinstalled reset and rescan the plug-ins http://www.cakewalk.com/S...ommended-for-Upgraders

Actually, it is X1 Studio 64bit.  I have both 32 and 64 installed.  When I tried it again, I checked under Help, About Sonar to make sure I opened the correct one, and it did identify it as x64, but CSC is not identified as 32-bit.  Most peculiar.
 
Thank you for your input and for going to the trouble of providing the links for me.