The drivers for the 7300GT are in the OS, the PCIe slots are backwards-compatible.
There is no reason why the 7300GT shouldn't work.
might not work since 7300gt probably is 32bit efi.
just as the 8800gt 32-bit efi version doesnt work in 64-bit macpro's.
The 7300GT won't work in 2008 and newer Mac Pros because of the 32/64 bit EFI changes. There were even 2 different versions of the 8800 card for Mac Pros, and they're not interchangeable.So, if nobody can tell me the 7300GT works in my mac pro 2010 (which was my only question), I will have to go for a GT120...