Hi,
I integrated the 3CX MyPhone with Outlook 2013 x86 on a Windows 8 Pro x64 OS and it is running without any problem.
So I think the 64 bit version of Office 2013 does not (yet) support the 3CX MyPhone plugin? Maybe v12 does.
BTW: You know the difference between the x86 and x64 editions?
Running the x64 (64 bit) edition also requires an x64 Windows edition. The advantages of Office x64 is a bit better performance. Disadvantage is that it doesn't support most third party plugins and add-ons. Microsoft actually discourages the use of the x64 editions. So unless you're absolutely sure you need an x64 edition, you should choose x86 (32 bit).