well most here and others who have had the 4600 will tell you that with all the bells and whistles turned on the 9500 Pro owns the 4600.
3D mark 01 wise score will prolly be close 4600 may even score a bit higher, but 3D 03 the 9500 Pro cause DX9.
I say get a 9700 and overclock it or flash it to 9700 Pro speeds. I am very happy with my 9500 Pro, it flat out ROX.
So I think you will see a gain the biggest being a 9700 Pro, next 9700 then 9500 non pro and convert it but thats not a guaratee to get 9700 speeds and for a very reasonable amount of cash the 9500 Pro retail card.
Cisco KId