It shouldnt make any difference, as far as i know there is no dx9 or dx11 versions, its just one format only that they stopped updating at v2.0 in 2014..
Gameguru works with .x as its ptimary import format and automatically converts it to .dbo itself. So its wont make much difference at all.
i7 7700,k NV1070 8GB, 16GB 3200mhz memory, 1x 2TB Hybrid, Win10.
i5 4760k, NV960 2GB, 16GB 2333mhz memory, 1x 2TB Hybrid, Win10.
i3, Intel 4000 series graphics, 6GB memory, 1x 500gb HDD, Win8.1.