This is your rig for SH3 and Chess only?
Your game will load fast with 16GB RAM - and then there will be no need to read anything from any disk again.
All components will have a lazy day and debate on the meaning of life.
You will be able to measure a difference with two HDs - but this will be no visible advantage - as the system with one HD should perform SH3 like a charm anyway.
It's a bit like asking if there is an advantage in shooting the cat with the 10,5 cm instead of the 8,8 cm.
The cat will be dead - and the splatter will be awesome - no matter the gun.