Hi and welcome to the Gigabyte Forum.
I haven't the size of the 470SO but I have the sizes for the cards next to it if that would help.
GV-N470SO-13I: H=42.5, L=291.1, W=126.9 mm
GV-N460OC-1GI: H=43, L=238 , W=130 mm
PSU size is dependant on the whole system so it is hard to say if yours will be sufficient. I would think it must be pushing it a bit though even with a fairly low end system.