Well, for one, the statement recarding Windows Server 2008R2 is wrong, unless you made just a typo with AMD64 here...
Sure it includes WOW64, but it needs 64-bit capable hardware, since it is only shipping as 64-bit O/S, aka x64.
And the fact that the OS is 64bit does in no way mean that your application has to be written in a 64bit compiler version as well...
Sure there are applications which are perfectly working as 32-bit application on a 64-bit system.
It is always depending on what your program does and how easy it is to implement natively.
If you are perfectly happy with WOW64 stay on 32-bit.
I write customization DLLs for a high end CAD application, so I am forced to support 64-bit.
The next release of the application is only supporting Windows 7 x64, due to memory consumption and other things.
A 32-bit version is still released, but if a problem is not reproducible on 64-bit it will hardly get fixed.